G08 



U. S. DEPARTMENT OF AGRICULTURE. 

BUREAU OF PLANT INDUSTRY— BULLETIN NO. 88. 

B. T. GALLOWAY, Chief of Bureau. 



WEEVIL-RESISTING ADAPTATIONS 
OF THE COTTON PLANT. 



O. F. COOK, 

BiONOMiST IN Charge of Investigations in the Agricultural 
Economy of Tropical and Subtropical Plants. 



Issued Janttaey lo, 190t>. 




WASHINGTON: 

government printing office. 

1906. 




J 

Book— 1^ € $ 



76 



S^l^ 






Bui. 88, Bureau of Plant Industry, U. S. Dept. of Agriculture. 



Plate I. 




U. S. DEPARTMENT OF AGRICULTURE. 
BUREAU OF PLANT INDUSTRY— BULLETIN NO. 88. 



B. T. GALLOWAY, Chiif i,f Bureau. 



WEEVIL-RESISTING ADAPTATIONS 
OF THE COTTON PLANT. 



O.^F. tOOK, 

BiONOMiST IN Charge of Investigations in the Agricultural 
Economy of Tropical and Subtropical Plants. 



Issued January 13, 1906. 




WASHINGTON: 

GOVERNMENT PRINTING OFFICE. 

liM)6. 



eff 



V •:•; :: 



BUREAU OF PLANT INDUSTRY. 

B. T. GALLOWAY, 

Pathologist and Physiologist, and Chief of Bureau. 

VEGETABLE PATHOLOGICAL AND PHYSIOLOGICAL INVESTIGATIONS. 

Albert F. Woods, Pathologist and Physiologist in Charge, Acting Chief of Bureau in Absence of Chief. 

BOTANICAL INVESTIGATIONS. 

Frederick V. Coville, Botanist in Charge. 

FARM MANAGEMENT. 

W. J. Spillman, Agriculturist in Charge. 

POMOLOGICAL INVESTIGATIONS. 

G. B. Brackett, Pomologist in Charge. 

SEED AND PLANT INTRODUCTION AND DISTRIBUTION. 

A. J. PiETERS, Botanist in Charge. 

ARLINGTON EXPERIMENTAL FARM. 

L. C. CoRBETT, Horticulturist in Charge. 

INVESTIGATIONS IN THE AGRICULTURAL ECONOMY OF TROPICAL AND SUBTROPICAL 

PLANTS. 

O. F. Cook, Bionomist in Charge. 

DRUG AND POISONOUS PLANT INVESTIGATIONS, AND TEA CULTURE INVESTIGATIONS. 

Rodney H. True, Physiologist in Charge. 

DRY LAND AGRICULTURE AND WESTERN AGRICULTURAL EXTENSION. 

Carl S. Scofield, Agriculturist in Charge. 

EXPERIMENTAL GARDENS AND GROUNDS. 

E. M. Byrnes, Superintendent. 

SEED LABORATORY. 

Edgar Brown, Botanist in Charge. 



J. E. Rockwell, Editor. 
Ja.mes E. Jones, Chief Clerk. 



INVESTIGATIONS IN THE AGRICULTURAL ECONOMY OF TROPICAL AND SUBTROPICAL 

PLANTS. 



SCIENTIFIC STAFF. 

j f(yi O lyUf o. F. Cook, Bionomist in Charge. 

G. N. Collins, Assistant Botanist. 
F. L. Lewton, Scientific A.isistant. 
H. Pittier, Special Agent. 



D.ofD. 



LETTER OF TRANSMITTAL 



U. S. Department of Agriculture, 

Bureau of Plant Industry, 

Office of the Chief, 
Washington^ D. C, September 26, 1905. 

Sir : I have the honor to transmit herewith a report on '' Weevil- 
Resisting Adaptations of the Cotton Phmt," and to reconniiend it 
for pnblication as Bulletin No. 88 of this Bureau. This report has 
been prepared by Mr. O. F. Cook, biononiist in charge of investiga- 
tions in the agricultural economy of tropical and subtropical plants. 
It contains an account of his observations and experiments which 
show that some of the varieties of the cotton plant have definite 
weevil-resisting characters. The establishment of these facts opens 
new and unexpected lines of approach to cultural solutions of the 
weevil i^roblem. 

The investigation of cotton referred to in this report was begun 
in March, 1904. through the Laboratory of Plant Breeding, there 
having been set aside for it from the emergency cotton boll weevil 
appropriation a part of the funds which had been devoted to the 
breeding of weevil-resistant cotton. The existence of a field culture 
of cotton in the presence of the boll weevil had been ascertained by 
Mr. Cook during a visit to Guatemala in 100"2, and it was hoped that 
the innnunity of the cotton might prove to be due to some weevil- 
resistant quality. 

The first result of detailed observations was the discovery of the 
weevil-eating kelep or so-called Guatemalan ant. which has been 
made the subject of previous reports through the Bureau of Ento- 
mology. It now appears that the usefulness of this insect is not 
limited to the boll weevils which it catches and kills. By making a 
regular field culture of cotton possible in the presence of the boll 
weevil it has contributed in an important manner to the development 
of the weevil-resisting characters here described. The cotton plant, 
it seems, has been greatly modified in protecting itself against the 
ravages of its insect enemy. Not only has it attracted the kelep to 
its service and developed other means of defense which are more 

3 



4 LETTER OF TRANSMITTAL. 

direct, but even the lint, on the Deculiar cliaracter of which the com- 
mercial value of the crop depends, appears to find its chief use to the 
plant in excluding the weevil larvse from the seed. Our Sea Island 
and Upland varieties have been raised for long periods in regions 
where the boll weevil did not exist and, as was to have been expected, 
are largely lacking in protective features. The Kekchi cotton, on the 
other hand, which has continued its development in a weevil-infested 
region under the protection of the keleps, has by far the largest 
number of weevil-resisting characters. 

The fact that weevil-resisting adaptations really exist, as shown in 
numerous instances in the present report, emphasizes the necessity of 
a thorough study of our cultivated cottons for the purpose of taking 
advantage of any and all protective characters. 

It is possible, as Mr. Cook suggests, that the Guatemalan variety 
of cotton which he has discovered, and Avhich has such a surprising 
number of weevil-resisting adaptations, may not prove suited to culti- 
vation in the United States, but even in that case the value of the 
present paper on weevil-resisting characters would not be diminished, 
for it will serve as a help to all who may engage in seeking and 
developing such characters in the types of cotton now cultivated in 
our country. 

Respectfully, B. T. Galloway, 

Chief of Bureau. 

Hon. James Wilson, 

Secretary of Agriculture. 



CONTENTS 



Page. 

Introduction . 7 

Selective iniinence of the boll weevil 10 

General protective characters 11 

Dwarf habit and determinate growth of Kekchi cotton 11 

Variations in the Kekchi cotton 15 

Effects of Guatemalan conditions on United States varieties. 17 

Acclimatization of Kekchi cotton in the United States 17 

Early bearing facilitated by long basal branches 19 

Early rejection of superfluous squares 20 

Seasonal bearing of perennial varieties 23 

Annual cutting back of perennial varieties 24 

Hairy stalks and leaf stems . 25 

Pendent bolls 27 

Extrafloral nectaries . 28 

Nectaries of the leaves 30 

External nectaries of the involucre . 31 

Inner nectaries of the involucre . 31 

Nectaries of Guatemalan Sea Island cotton 32 

Continued secretion of nectar 32 

Brac'tlets subtending inner nectaries 33 

Efficiency of the kelep protection 34 

Other nectar-bearing plants visited by the keleps 36 

The involucre as a protective structure 37 

Involucral bracts grown together 37 

Appressed margins of bracts _._..-. 38 

Large involucres of Kekchi cotton 39 

Opening, or flaring, of bracts avoided 40 

Hairy margins of involucral bracts . 41 

Extent of protection by involucre . . : . . . 41 

Advantage of open involucres 42 

Behavior of parasitized buds 43 

Shedding of weevil-infested squares ... 43 

Cotmtings of flared and fallen squares 45 

Prolifc ration of internal tissues of buds 46 

Causes and conditions of bud proliferation 49 

Proliferation in other varieties 50 

Protection of the bolls 51 

Persistence of flowers 51 

Immunity of very yovmg bolls 52 

Rapid growth of young bolls . 55 

Thick- walled bolls . 56 

Tough linings of chambers of bolls 56 

5 



6 CONTENTS. 

Protection of the bolls — Continued. Page. 

Proliferation from the wall of the boll 58- 

Time required for proliferation 60 

Efficiency of adaptive characters of bolls 61 

Bacterial diseases following weevil injuries 62 

Breeding in buds a derived habit 62 

Relation between proliferation in buds and in bolls 64 

Protection of seeds by lint . . 65 

Protective seed arrangement in Kidney cotton 66 

Cultural value of Kidney cotton 67 

The nature and causes of adaptations 67 

Conscious and imconscions selection 70 

Summary of adaptations 73 

Classification of adaptations 72 

Adaptive characters of different types of cotton 73 

Concluding remarks 74 

Description of plates 78 

Index 79 



ILLUSTRATIONS 



Plate I. Valley at Secanqnim. Alta Vera Paz. Guatemala, the scene of 

experiments with weevil-resisting cotton Frontispiece. 

II. Fig. 1. — Mature plant of Kekchi cotton. Fig. 2. — Kekchi cotton 

plant with bolls 78 

III. Involucres of Kekchi cotton, showing nectaries and bractlets 78 

IV. Fig. 1. — Involucres of Rabinal cotton, showing connate and ap- 

pressed margins. Fig. 2. — Open involucres of Egyptian cotton. 78 
V. Fig. 1. — Young buds of Kekchi cotton with weevil punctures. 

Fig. 2. — Buds of Kekchi cotton with proliferation 78 

VI. Large buds of Kekchi cotton with jorolif eration 78 

VII. Weevil-infested bolls of Kekchi cotton 78 

VIII. Carpels of Kekchi cotton, showing proliferation 78 

IX. Fig. 1. — Kekchi cotton, successive stages of the boll. Fig. 2. — 

Kekchi cotton bolls (right) compared with King bolls (left). .. 78 
X. Fig. 1. — Rabinal cotton with bolls. Fig. 2. — Bolls and seeds of 

Kidney cotton _ _ . 78 



B. r. I. — ISO. 



WEEVIL-RESISTING ADAPTATIONS OF THE 
COTTON PLANT. 



INTRODUCTION. 

The fact that Central American varieties of cotton have developed 
weevil-resisting adaptations has already received preliminary notice." 
A third visit to Guatemala, in the spring of 1905, has given opportu- 
niity for further studies of the protective characters of the native 
varieties and for comparing them with the types of cotton now cul- 
tivated in the United States. For this purpose plantings of Upland 
and Sea Island varieties have been made in Guatemala, and as the 
season advanced other tests of the Guatemalan and United States 
varieties were arranged under very ditferent climatic conditions in 
Texas and at "Washington. 

These opportunities of comparative observation have revealed a 
series of protective adaptations of such number and nicety as to fur- 
nish a unique and well-nigh incredible instance of selective develop- 
ment. The statement of the former paper may be repeated with 
emphasis, that the presence of the weevil-eating kelep has enabled 
the Indians of eastern Guatemala to maintain since very ancient 
times field culture of cotton in the presence of the weevils, with the 
result that there has been developed a dwarf, annual, short-season 
variety with numerous features which, in the absence of sufficient 
numbers of keleps, afford material assistance in protecting the crop 
against the ravages of the weevil. 

Wliether this Guatemalan cotton can be made of direct use in the 
United States or not, it demonstrates the existence in the cotton 
plant of weevil-resisting characters. The new variety has lint of 
good length and quality, so that its utilization in the United States 
depends upon its adaptability to our climate and methods of culture. 

As already explained in publications devoted to the kelep, the 
weevil-eating propensities of that insect were discovered in 1904: 
during a visit to Guatemala which had been undertaken in the hope 
of finding a w^eevil-resisting variety of cotton. It had been observed 

a Cotton Culture in Guatemala. Yearhook of the Ignited States Department of 
Agriculture for 1904, 475-488 ; Science, N. S., 20 : GG6-G70. November 18. 1904. 



8 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

two years before that a field of chvarf cotton cultivated by the Indians 
did not suffer from the boll weevils, though these pests were abundant 
on a " tree cotton " a short distance away. 

The kelep afforded an entirely unexpected and yet very striking 
explanation of the fact that cotton was being grown as a regular 
field crop in a region which had probably been infested with weevils 
for many centuries, if it were not, indeed, the original home of the 
species. That there Avas an insect in existence specially qualified 
by structure and habits to attack, disable, and devour the boll weevil, 
was Avelcome news in the United States, and in accordance with cabled 
instructions from the Secretary of Agriculture numerous colonies 
of the keleps Avere brought home and colonized in the cotton fields 
of Texas. 

The finding of the kelep explained the failure of the weevils to 
prevent cotton cultivations in eastern Guatemala, and seemed at first 
to diminish the prospects of weevil resistance in the cotton itself. 
Nevertheless, the intention of studying Guatemalan varieties of cot- 
ton and the cultural methods in use in that country was not aban- 
doned, and the residts are not without bearing on the original ques- 
tion of the causes of the apparent immunity of the Guatemalan 
cottons, and also upon the more practical question of securing cotton 
varieties and cultural methods by which the injuries of the boll 
weevil in the United States may be reduced to a minimum. 

The Guatemalan cotton protected by the keleps is a genuine Ujd- 
land variety, very early and productive, with a fiber of good length 
and texture, as already stated. In addition to features which di- 
rectly favor the keleps, it has many other qualities which may 
render it useful, even without its insect guardians. In former reports 
it has been compared with the very early Upland varieties, such as 
King and Parker; but comparative tests made in eastern Guatemala 
show that the native variety, which it is proposed to call Kckchi^ 
represents a very distinct type of this important cultivated plant. 
It belongs to Gossypium hirsutinn, the Upland species or series of 
varieties, in the sense that it is not a Sea Island, Egyptian, or Kidney 
cotton,"' but it is distinctly more different from any of the Upland 
varieties now cultivated in the United States than these are from each 
other. It has not been ascertained that the Kekchi cotton in its 

o The Sea Island cotton is so called because cotton of this type is cultivated 
on the Sea Islands of South Carolina, lonjj famous for the excellence of their 
product. The Sea Island cotton came origlnall.\' from Barbados, whence also 
its botanical name, Gossypium barbadensc. 

Upland cotton gained its name as a means of distinguishing it from the Sea 
Island, being cultivated in the interior, or " upland." districts of the Southern 
States. The Upland type of cotton was recognized as a distinct species by 
Linnjeus under the name Gossypium hirsutum, but many subsequent writers 



INTRODUCTION. 9 

present form is suited to cultivation in the United States, but it has, 
without any doubt, new and significant characters which must be 
regarded as factors in cultural solutions of the weevil problem. (PL 
ILfig. 1.) 

Although cotton was not found to be planted as a regular field cul- 
ture in any localities in (juateniala where the keleps do not exist, 
small quantities are produced in the interior plateau region about 
Ivabinal by what may be called dooryard cultivation, and these, too, 
have suggested cultural factors and expedients which may not be 
without practical bearing. 

The present paper can claim to make only a beginning in the 
bionomic t-tudy of the question, but it shows at least that the weevil 
problem has many avenues of approach on the botanical side. 

The cotton of (ruatemala and neighboring countries has maintained 
an existence, at least, in the presence of the weevils, and has suffered 
an acute natural selection with reference to its ability to protect itself 
against the weevil or to secure the assistance of allies, such as the 
keleps. That no commercial cotton crop is raised or exported from 
such districts does not prove that they are unworthy of scientific 
investigation, or that they are not likely to yield materials and sug- 
gestions of practical value in meeting the invasion of Aveevils which 
is now so serious a menace to the cotton industry of the United States. 
'Some of these Aveevil-resisting adaptations have been of use in 
securing for the cotton the assistance of the keleps. There are others 
which, if properly utilized, might render these interesting insects 
unnecessary. Tropical America has been serving for thousands of 
years, evidently, as ^i laboratory for this class of experiments. Texas 
Avas invaded only yesterday — a decade ago. Now that we are forced 
to engage in the strife, the first preliminary should be, it would seem, 
to take stock of the weapons Avhich nature has forged. 

The present report was planned and partly written before the dis- 
covery of the true nature of the best of the Aveevil-resisting adapta- 
tions — the proliferation of the tissues of the buds and bolls. Some 
of the characters here described may have no value except as sug- 
gestions, but taken together they may be of interest as an outline of 
the results of the very long period of selection to which the presence 
of the boll Aveevil has subjected the Central American varieties of 
the cotton plant. 

have erroneously confused it with tlie Old World species Go^syplum herhaccnm, 
wbifh is- not cultivated in the United States, though often so reported. 

The Egyptian and Kidney cottons belong to the Sea Island series, and are of 
American origin. The Kidney cottons seem not to have been cultivated on a 
conmiercial scale, but they are very widely distrilmted in tropical America. The 
name refers to the fact that the seeds rf each comi)artment of the boll are 
grown together into a small comjiact mass, in shape suggesting a kidney. 



10 WEEVIL-KESISTING ADAPTATIONS OF COTTON. 

SELECTIVE INFLUENCE OF THE BOLL WEEVIL. 

The boll \A'eevil exerts a most prejudicial eliect upon the cotton 
crop, but, unlike most parasites, it does not cause disease or debility 
in its host plant. The young buds and bolls are merely pruned away, 
as it were, the purposes of the weevil being the better served when the 
plants remain vigorous and continue to produce more buds and bolls, 
in which more eggs can be laid and more larvae brought to maturity. 
Nevertheless, if no bolls are allowed to develop no seed can be set. 
The fate of the cotton crop in wet seasons in Texas shoAvs that with- 
out some form of protection the plant would have been extinct long 
since in all localities reached by the boll weevil. 

The long contact between the boll weevil and the cotton plant in 
Central America has given ample opportunity for the latter to profit 
by the selection which the insect itself has provided. Every differ- 
ence by which a cotton plant was able to resist or to avoid the weevil 
and thus ripen more seeds than its fellows would give it a distinct 
advantage, quite as if the selection were consciously carried on by the 
planter or the plant breeder. The case is different from that of the 
recent improvements of man^^ of our cultivated plants by selection 
for the increase of some particular quality already existing. Such 
improvements can often be made appreciable, or even highly valu- 
able, in comparatively few years, but under the desultory Indian 
methods of cultivation long periods of time would be required for 
the origination and accumulation of such characters as these pro- 
tective adaptations. 

Climate and other local conditions must also be taken into consid- 
eration. An adaptation which would be effective in one set of cli- 
matic conditions may be of little use, or even a positive disadvantage, 
in others, as, for example, the prompt shedding of the parasitized 
buds. In a dry region the falling of a bud to the superheated, 
sun-baked earth insures the death of the weevil larva, either by the 
heat directly or by the complete drying out of the tissues in which 
the larva is embedded. In the moist districts of eastern Texas, how- 
ever, this expedient is quite ineffective, the larvae often developing 
even better when the buds fall off and lie on moist soil than when they 
remain attached to the plant. 

It need not surprise us to learn also that the weevil-resisting adap- 
tations shown by the Kekchi and other cotton varieties of Central 
America are shared, to some extent, by those already known in the 
United States, since the whole Upland type of cotton appears to have 
been, originally, a native of the Central American region. Varieties 
which reached the United States from Mexico and the West Indies 
may, however, have had little or no contact with the weevil for many 
centuries, while in Central America the struggle for existence has 
remained severe and continuous down to the present day. 



GENERAL PROTECTIVE CHARACTERS, 11 

It is now known that in the plateau region of jMexico the long dry 
season eli'ectnall}' excludes the weevil, so that varieties of cotton from 
the Mexican highlands, instead of being weevil-proof, as sometimes 
represented, may have no immmiity whatever Avhen brought into 
the much more moist climate of the cotton belt of the United States. 

The Kekchi cotton of Guatemala, on the other hand, has to a much 
greater degree than any of the varieties now grown in the Ignited 
States the very qualities which experiment has shown to be effective 
for the mitigation by cultural means of the injuries inflicted by the 
boll weevil. That it has, in addition, other features not possessed 
by our United States varieties, or not hitherto interpreted as weevil- 
resisting adaptations, need not be looked upon as anything outside 
the normal order of nature, but is entirely in accord with what 
appears to l)e the biological and agricultural history of the cotton 
plant in Central America. 

GENERAL PROTECTIVE CHARACTERS. 

DWARF HABIT AND DETERMINATE GROWTH OF KEKCHT COTTON. 

Although Guatemala is a tropical country and the climatic condi- 
tions are suitable for the growth of cotton throughout the year, the 
Kekchi cotton is cultivated only as an annual, and is smaller and 
more determinate in its habits of growth than the Upland varieties 
now known in the Ignited States. It soon attains its full height, 
and after a crop of bolls has set on the lower branches there is a 
definite tendency to cease growing or producing new buds. The 
later upward growth of the plants seems to be supplementary, as it 
were, to the formation of the bolls; often there appear to be no 
more flowers formed, and many of those which come seem to be 
undersized, as though the plant were really mature and were 
approaching the natural termination of its existence. Our Upland 
varieties, on the contrary, continue to produce throughout the season 
hundreds of small squares on each plant which serve only as breed- 
ing places for the weevils. 

The explanation of the high development of these short-season 
qualities of the Kekchi cotton is doubtless to be found in the custom 
of the Indians, who pull up the cotton as soon as the bulk of the crop 
has ripened to make room for the peppers, which are always planted 
with the cotton. For the Indians the peppers are an even more 
important crop than the cotton, so that when the time comes for 
clearing away the cotton they do not wait for the plants which may 
have delayed maturity. Late bolls, even, would ncA-er come to 
maturit}^ or furnish seed" for planting. The result has been a very 
long-sustained selection for early bearing and uniform ripening of 
the crop. Some of our earliest Upland sorts may begin blossoming 



12 WEEVIL-RESISTfXG ADAPTATIONS OF COTTON. 

as soon as the Kokclii, but they show far less tendency to determinate 
growth. 

The development of earliness has been assisted, no doubt, b}' the 
(?limatic conditions which prevail in eastern Guatemala. The rainy 
season oftens begins before the cotton harvest is completed, so that 
the later bolls are very likely to become diseased, or, if they reach 
maturity and open, the lint is often beaten to the ground and made too 
dirty for use in spinning and weaving. In either case the seed is not 
harvested. 

The Indians believe that even if they did not pull the cotton up it 
would not become a perennial, but would die out completely, even to 
Uie roots, during the rainy season. Seeds scattered accidentally in 
the plantation at harvest time are rotted by the rain and do not germi- 
nate, so that little or no volunteer cotton is carried over from one 
season to another. 

If the Kekchi cotton Avere the onl}' variety planted in Guatemala 
and the weevil had there, as in the United States, no other food plant 
than the cotton, the insects might all die oi!' between April or May, 
M'hen the cotton is pulled up, and October, when the next crop is 
planted. There is, however, enough perennial '' tree "" cotton in the 
countrj^ to keep the pest from becoming exterminated. ^loreover-, 
the question of additional food plants in Guatemala is still open. 

The importance of securing short-season varieties of cotton for the 
United States can hardl}^ be overestimated, since, as already intimated 
elsewhere," there is no longer any reason to hope that the more severe 
winters of the northern districts of the cotton belt will give any pro- 
tection against the weevils. 

As long as the weevil was confined to the southern part of Texas, 
Avhere the cotton could survive the winter, the destruction of the 
plants as soon as possible after the maturing of the crop Avas the only 
measure calculated to seriously reduce the number of weevils. It 
w^as also essential to plant cotton as early as possible in the spring to 
aA'oid the Aveevils bred on the volunteer, or hold-over, cotton Avhich 
negligent planters had left in the ground. The extension of the pest 
farther north and the possibility of securing cotton varieties with 
determinate habits of growth introduce several new considerations. 
The hold-over cotton is eliminated from the problem, but in the more 
northern latitudes, Avhere the cold comes earlier and the temperature 
remains loAver throughout the winter, it may often happen that there 
will be no period in Avhich the weevils can l)e reduced by starvation, 
unless time can be secured for this purpose in the spring by the i^lant- 
ins: of short-season varieties of cotton. 



a Cook, O. F., 1905. Progress iu the fotuuy of the Kelep, Science, N. S., 21 : 
552. 



PROTECTIVE CHARACTERS OF KEKCHI COTTON. 13 

Instead of colder winters being unfavorable to the Aveevils, there is 
every probability that cold sufficient to keep them in a torpid, inactive 
condition will jDreserve their noxious lives much better than warm and 
pleasant weather, which enables them to continue active and thus 
deplete their vital energies. The winter of 1904-5 was one of un- 
precedented severity in Texas, both in absolute temperature and in 
continued cold and wet, and yet the weevils were able, in many locali- 
ties, to infest heavily the early plantings of cotton to a far greater 
extent than in previous years. 

The farther north the locality the more will the efficiency of cul- 
tural methods of avoiding tlie boll AA-eevil depend upon the plant- 
ing of quick-maturing varieties of cotton. It is true that in a 
favorable season the cotton planted first would set its crop soonest, 
and thus escape a part of the damage suH'ered by adjoining fields 
of later growth, the earlier fields breeding weevils to attack in 
larger force the later plantings. But instead of insuring a decrease 
of the number of weevils in a given locality and checking the 
propagation of the pest, very early planting by a part of the farmers 
of a community might tend, after an early fall and a cold winter, 
to the opposite result, since it would save the lives of large numbers 
of weevils which would otherwise perish before the cotton, if sown 
a few weeks later, would be large enough to furnish the Aveevils 
with food. Dr. Herbert J. Webber states that planting could 
probably be deferred even to the middle of June without impair- 
ing the chances of a crop as large as that which can be obtained 
in the presence of the weevil. 

There Avould seem to be little object in planting cotton Avhere 
the weevils are as abundant as in some places in southern Texas in 
the spring of the present year, 1005. Xevertheless, the opportune 
occurrence of a few weeks of dry weather was able, even then, to 
greatly improve the prospects of a crop. No matter how bad the 
weevils, the planter still has hope that dry weather may come and save 
his crop from being a total loss. As long as indeterminate varie- 
ties are planted this possibility will always make it difficult to carry 
out a general policy of early destruction of the plants. 

Some of our Upland varieties of cotton are early enough in the 
sense that they begin flowering and fruiting very promptly, but 
unless the season is very dry they will produce a continuous succession 
of buds until they are pulled up or frost cuts "them off. The earli- 
ness of practical value is not to be shown merely by the date of 
flowering, but by the date of ripening the crop of bolls and of 
ceasing to form new buds in which weevils can breed. If the im- 
provements noted in other parts of this report can be realized in 
practice, it would no longer be necessary to destroy the cotton plants 



14 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

in order to put an end to the breeding of the weevils. It would 
then become practicable and desirable to regulate planting so as to 
bring the growing period of the cotton at the most favorable season 
for a rapid development of the crop, and thus to give the weevils 
the shortest possible opportunities for breeding." If the fall and 
Avinter had favored the survival of many weevils, planting could well 
be deferred until the weevils had disappeared, a fact which could be 
ascertained by starting early a few observation plants from which 
the weevils could be carefully picked by hand as long as they con- 
tinued to appear. 

The extent of the mortality of the boll weevil in the spring has been 
well shown in the investigations reported by Mr. W. D. Hunter on 
tlie etfects of applying Paris green to the very young cotton as a 
means of destroying the weevils Avhich had lived through the winter. 
Numerous dead weevils were found in the poisoned fields, but equal 
or even greater numbers were found in those to Avhich no Paris green 
had been applied, and the conclusion Avas drawn that a large propor- 
tion of the weevils, which pass the winter in a state of hibernation 
or torpidity induced by the cold, perish through starvation or other 
causes in the spring, after the weather has become warm enough to 
render them active again and permit them to renew their search for 
cotton plants on which to feed and lay their eggs.'' 

It is easy to understand, too, that after the weevils have been re- 
duced by the cold to a condition of inactivity involving an almost com- 
plete suspension of the vital functions, the lack of food and the lapse 
of time can make very little difference with them. Starvation comes 
much quicker during Avarm Aveather while they are going actively 
about, so that it is the autumn and spring which must be relied upon 
to reduce the numbers of the weevils rather than the cold periods of 
the Avinter months. Messrs. Hunter and Hinds haA'e also noted as 
significant the fact that of AveeA'ils captured at the middle of Decem- 
ber, 15.8 per cent passed the Avinter successfully, Avhile of another lot 
captured a month earlier, only 1 per cent survived. Their conclu- 
sions were as folloAA^s: 

It is evident that the \A'eevils wliicli pass tlie winter and attack the crop of 
the following season are among those developed latest in the fall and which, in 
consequence of that fact, have not exhausted their vitality by oviposition or any 
considerable length of active life. 

With these facts in mind it becomes plain that no objections need 
be raised on general biological principles to the introduction of new 

"A determinate variety of cotton would also avoid the cultural disadvan- 
tages incidental to very early planting, for if the weather happens to turn 
cold and wet the cotton is often either killed outright and has to be replanted 
or, what is still worse, it becomes permanently stunted and unproductive. 

6 Hunter, W. D., 1904. The Use of Paris Green in Controlling the Cotton Boll 
Weevil, Farmers' Bulletin No. 211, U. S. Department of Agriculture. 



VARIATIONS IX KEKCHI COTTON. 15 

quick-miituring varieties of cotton from tropical countries on the 
ground that cold weather will exclude them from the United States. 
The early spring is the only time in which they will be likely to 
encounter adverse conditions in this respect, and if varieties can be 
secured which are able to mature a satisfactory crop in a short season^ 
these quick-maturing qualities will far more than compensate for any 
lack of ability to withstand cold weather in the early spring. 

The Kekchi cotton may prove, however, to be quite as tolerant of 
cold as the other Upland varieties now cultivated in the United 
States." In its native country it is planted in October and grows 
throughout the Avinter months in mountain valleys where tempera- 
tures of between 40° and ()0° F. are not infrequent. (PI. I.) 

VARIATIONS IN THE KEKCHI COTTON. 

Very great diversity of size, habit of groAvth, and other features 
exists in the Indian cotton of the vicinity of Secanquim and Cajabon. 
The plants cultivated by Mr. John H. Kinsler on the United States 
system were also very different from any grown by the Indians, 
being much more robust and compact than in the more crowded 
native fields. The spreading lateral branches and low, compact 
growth of the Kekchi cotton, as shown in Plate II. figure 1, might have 
cultural, disadvantages if these tendencies were to be maintained in 
regular field cultures. Such, however, is not likel}^ to be the case. 
AVlien growing closer together the plants are more upright and less 
leafy below. 

To wdiat extent the differences observed thus far represent varietal 
characters can scarcely be determined without a field test of the 
apparently different strains, side by side. The broken, precipitous 
nature of the country renders it impossible to rely upon comparisons 
of the conditions of the different fields. 

The conservative agricultural habits of the Indians would tend to 
the continued planting by one man or family of the same seed for 
long periods of years, wliich might well conduce to the formation of 
separate strains. The low germinating power of the seed may pos- 
sibly be due to such inbi-eeding, though it is more likely that it deteri- 
orates because of the humidity of the climate.'' Xevertheless, our 
experiments were sufficient to prove that even among plants grown 
from seed raised by the same Indian there were very appreciable 

a This was shown to be a fact before the report was printed. See p. 18. 

& The Indians appreciate the fact that the cotton seed does not germinate well. 
They are accustomed to plant six seeds together, from which two or three plants 
usually reach maturity, often with one or two insignificant dwarfs underneath. 
The yield per plant in these crowded fields is naturally very small, but the larger 
individuals often bear from 20 to ?>0 bolls. At Rabinal from fi to 10 plants in a 
cluster is the rule, the product of the individual being still further reduced. 



16 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

differences, sufficient to liave a very practical bearing upon tlie ques- 
tion of securing strains having the special characters required in the 
United States. Indeed, there was nearly as much diversity anions 
the Guatemalan plants as among all the Upland varieties, though 
these were in some cases unusually variable, as a result apparently 
of the transfer to ncAV and unwonted conditions of climate and soil. 

The usual number of locks or cells in a boll of the Kekchi cotton is 
four, but bolls containing three or five are not uncommon ; often they 
are on plants which have otherwise the usual number. 

There is also considerable diversity on the same plant in the shape 
of the bolls, some, for example, remaining quite conical and pointed, 
Avhile others round out to near the apex. One plant was observed 
in which the bolls were very nearly spherical. The involucre was 
also unusually large. The plant had an unusually deep red or black- 
ish color, and was distinctly more vigorous than its neighbors, as 
often happens with mutations. 

It is not at all probable that a close selection has ever been prac- 
ticed by the Indians, so that a Avide diversity of mutational charac- 
ters may be exj^ected when once the varietv has been brought under 
careful observation. 

The stems and petioles of the Kekchi cotton plant are dark red, 
or at least spotted Avith red. and the leaves turn dull red Avith matu- 
rity. The bracts and bolls are green Avhen young, but Avith age and 
exposure to the sun become more or less tinged or spotted Avith reel." 
The outer iuA'olucral nectaries also turn deep red, especially the tAvo 
upper ones, eA'en Avhile the buds are still A-^ery young. The great 
majority of the leaA'es are simply three-pointed, but*many of them 
liaA'e an additional smaller lateral point on each side near the base. 

a One plant at Secanquim showed a Aery decided instance of A-ariegation 
A\-ith white and red. though the latter color might haA-e been due to an increased 
tendency of the AAhite portions to take the red discoloration common on normal 
leaA-es. The lower branches of the plant show only normal green coloration, 
and a part of the upi)er branches is also normal in color and size, and \Aith 
fruits rather above the aAerage size. The A-ariegated branches do not regu- 
larly alternate, nor do they come all from one side, but they might still haA'e 
connection with the phyllotaxy. There seem to be two stages of the A'ariega- 
tion, a white and a light greenish-yellow; the latter may belong only to young 
leaA-es. Both are distributed with the utmost irregularity, and both may 
affect the upper surface of the leaf while the under surface remains green, or 
A'ice A'ersa, though the latter condition is much less common than the former. 
The etiolated portions of the leaA'es. InA-olucres, and fruits do not attain the 
full size of the corresponding normal organs, so that the parts affected are 
more or less unsymmetrical, though where the A-ariegation is slight this result 
may be apjiarent, or if It be complete the symmetry is not affected. Except 
for two premature bolls the seed was not ripe, and these AA'ere from the nor- 
mal lower part of the plant. 



ACCLIMATIZATION OF KEKCHI COTTON. 17 

KI'I'Kl TS OF (;l ATKM AI.AA COX DITION.S ON I'NITEI) STATES VARIP:T1ES. 

The behavior of the United States varieties under changed climatic 
conditions in (rnateniahi is interesting in several ways. The '" King," 
which in the United States appears to resemble the Guatemalan 
variety most nearly, here loses most of its distinctive characters and 
breaks np into a variety of types, many of which wonld not be recog- 
nized in the United States as at all related to King. One of these is 
a " limbless " or " cluster ^ variety, which for a time appeared to 
Mr. Kinsler as a very promising new sort. It was smaller and dis- 
tinctly earlier than King ])lants of the normal type, and seemed 
likely to be more i)rodnctive. but only a few bolls developed, and 
these [)roved to be of abnormal form, with deep grooves or notches 
across the ti]). 

One of the features in which the change of climate seems to pro- 
duce remarkable eft'ects is that of earliness. The King, which in the 
States is looked upon as the earliest variety, is found by Mr. Kinsler 
to be somewhat exceeded in this respect by " Allen,'^ Avhich has not 
been looked upon as a competitor. The Sea Island and Egyptian 
varieties, too, prove to be much more precocious than was expected. 
Some of them begin floAvering almost as soon as the Upland sorts. 
The Rivers variety of Sea Island cotton, in particular, was very 
early, robust, and productive, distinctly ahead of the near-by Janno- 
vitch, though not so tall. 

ACCLIMATIZATION OK KEKCHI COTTON IN THE UNITED STATES. 

It was not unexpected that the Kekchi cotton would show a change 
in its method of growth on being transferred to Texas. New condi- 
tions of soil and climate often cause notable disturbances of the 
organism. Some of the tropical cottons planted in Texas for experi- 
mental purposes have grown into large bushes Avithout shoAving the 
slightest tendency to produce fruit or even floAvers. In lOO-t cotton 
from Peru planted at Victoria, Tex., grew most Aagoro.isly to a 
height of 18 feet, but remained quite sterile. It is possible, hoAvcA-er, 
that even in their oAvn country these Avere Avhat are called " tree 
cottons," Avhich usually groAv to considerable size before beginning 
to floAver. Letters from Mr. Kinsler, in charge of our exi)erimenta] 
plot at Pierce, Tex., relate a similar behaAaor on the part of the 
Kekchi cotton, Avhich at that place has groAA^n large and rank; but 
toward the end of July it Avas beginning to fruit, so that the ripening 
of seeds in Texas is to be anticipated. 

Two or three years will probably suffice to diminish this abnormal 
vegetative vigor, due to the stimulus of the ncAv conditions, and per- 
mit a return to the normal earliness of the variety. Similar results 
9962— No. 88—05 m 2. 



18 wep:vil-reststing adaptations of cotton. 

have attended the introduction into Texas of Mexican varieties of 
corn. The phmts grew 1 ! feet higli the first year and bore very littk; 
seed; in the foUowing seasons they became smaller, earlier, and more 
productive. 

The probability that the Kekchi cotton can be grown even at the 
northern limits of cotton cultivation is strongly indicated by the 
results of an experiment at Lanham, Md. (1905). In favorable sea- 
sons cotton can be grown to maturity as far north as AVashington, but 
the present year has been very unfavorable, the suunner months being 
for the most part cool and rainy, and with several intervals of 
unusually low temperature. The cotton, which was planted intention- 
ally in rather poor soil, to avoid too great luxuriance of growth, ger- 
minated very badly and remained small and stunted until August. 
The Kekchi rows have, however, produced more plants, and more of 
these have grown to maturity than with any of the domestic or for- 
eign varieties included in the test. The Kekchi type has also remained 
more constant in Maryland than did the King variety when grown in 
Guatemala, though there are obvious ditfereuces between individual 
plants. Tw^o plants in particular were found to have numerous buds, 
some ready to blossom before any of the others had begini to show 
signs of productive maturity. 

It might be feared that a variety newly introduced from a tropical 
country would be likely to suffer more from low temperatures than 
our United States varieties, but this seems not to be the case with the 
Kekchi cotton, even w'hen the cold is carried down to the freezing 
point. There were light frosts in Lanham about the end of Septem- 
ber, just sufficient, as it happened, to do appreciable damage to cotton 
in low ground. The Kekchi plants did not suffer more than the 
American Upland varieties. The difference, if any, was in favor of 
the Kekchi cotton, perhaps on account of the closer foliage. 

Many annual plants, even those of tropical origin, are most vigor- 
ous and productive at their northern limits of growth, not, as has l)een 
supposed, because this is the coldest part of their range, but l)ecause 
the heat and sunlight, necessary to plant growth, are greater during 
our summer months than can be secured in a sinular time in the 
Tropics, owing to the nuich longer days of our northern latitudes." 

The Pachon cotton from western Guatemala, though it has grow'n 
taller at Victoria, Tex. (52-79 inches), than at Lanham, Md. (30^0 
inches), has produced numerous buds in Maryland, but none in 
Texas. The Kekchi cotton also appears to have been more productive 
at Lanham than at Victoria, to judge from a recent partial report 
from Mr. Argyle McLachlan. 



a Cook, O. F., 1902. Agriculture in the Tropical Islauds of the United States, 
Yearbook of the United States Department of Agriculture for 1901, p. 367. 



EARLY BEARING AIDED BY LONG BASAL BRANCHES. 19 

It is very possible, therefore, that if the (iiuitenialiiii variety is able 
to thrive^n the United States it will ripen its crop here in even less time 
than it re(i[uires in Gnateniala, and this is rendered the more probable 
from the fact that in Guatemala the cotton has to be planted in the 
rainy season and is obliged to exist for the first few months under 
conditions of excessive moisture. The dry season of this district is 
short and uncertain. For two years, 1908 and 1004, the Indians were 
miable to burn their clearings, so that the corn crop failed and the 
connnunity was reduced to the verge of starvation. The cotton crop, 
in jiormal seasons, is said to be planted in the latter half of October 
and ripens in March. 

The introduction of a dwarf, short-season cotton woidd i-e()uire, of 
course, something of a change in cultui'al methods in the South, since 
the smaller size of the plants will ueed to be comi^ensated by closer 
l)lanting. It Avill l)e readily understood that to secure the setting of 
a crop in the mininunn of time as many plants as possible should 
be set at work. The question is not that of the maxinunn product for 
each plant or for a given area. AVith the weevil in the field the time 
factor becomes of chief importance. 

Little is gained in reality by the rank growth of the largei- vai-ie- 
ties; in fact there is a distinct loss in earliness, even though some 
bolls are set in the early part of the season. If these are overshad- 
oAved and starved by the continued upward growth, the crop is delayed 
and the lower part of the plant becomes, on the whole, distinctly 
unproductive. 

EARLY BEAR1N(; EACILITATED BY LONG BASAL BRANCHES. 

The earliness of the Kekchi cotton is made possible by the fact that 
the bolls are nearly all borne at the base of the plant, the upper 
branches and their foliage serving merely to assist in bringing to 
maturity the fruits which are set while the plant is still very young. 

Like several other tropical economic species, such as coffee, cacao, 
and the Central American rubber tree, the cotton 2:)lant has tAVo kinds 
of branches — the true or })rimary branch, Avhich arises in the normal 
position of branches in the axil of the leaf, and the secondary or fruit 
branches, one of Avhich arises at the side of each primary branch. In 
most A^arieties only a fcAV of the true branches are deA'eloi)ed; often 
none at all. They are almost ahvays plainly indicated, hoAvever, by 
a small bud or a stunted leaf or tAvo, in case the bud has not remained 
entirely dormant. 

Cotton plants are either right-handed or left-handed in the sense 
that on the same plant all the secontlary branches come out on the 
same side of the primary branches. It is possible, therefore, to de- 
termine by its position whether any particular branch is a primary or 



20 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

a secondary. But the function of tlic two sorts of l)ranchcs does not 
alwaA's remain as distinct as in the cotfee and cacao. A primary 
branch, like the main stem, never bears any flowers; it prochices only 
leaves and other branches, mostly secondary. 

Secondary l)ranches, on the other hand, produce normally a flower 
bud at the axil of each leaf, and this rule holds very generally, except 
that at the lower part of the plant it sometimes happens that a branch 
which has the secondary position functions as a primary; that is, 
instead of bearing buds and flowers it produces only leaves and sec- 
ondary branches. In the Kekchi cotton, as grown crowded together 
in the Indian fields, the prinuiry branches seldom a})pear, but when 
more space is allowed and the soil is fertile it is usual for two branches 
to start from the axil of each of the lower heaves, one promptly i)ro- 
ducing flowers, the other assisting in the rai)id increase of the leaf 
surface of the plant and of its power to elaborate food. 

Under the ])opular idea thirt plants draw their food from the 
ground the possession of branches which bear little or no fruit might 
be looked upon as an undesirable character, but when we take into 
consideration the fact that the leaves instead of the roots are the true 
assimilating t:)rgans of the plant it becomes apparent that a variety 
of cotton which develops its lower primary branches ma}^ have an 
advantage in earliness over one which is obliged to depend for its 
foliage upon secondary or fruit-bearing branches. In the matter of 
determinate habits of growth these primary branches are also a fea- 
ture, because they enable a plant to produce a full quota of leaves 
without unduly increasing the number of fruiting branches and thus 
continuing to add to the number of superfluous buds. 

The most obvious characteristic of the Kekchi cotton as it grows in 
our experimental plots is the long basal branches, Avhich often equal 
or exceed in length the main stem itself. The most prolific branches 
of the United States varieties are those Avhich come out from the main 
stem at the height of about a foot, but the bulk of the crop on the 
Kekchi cotton is borne much closer to the ground. (PI. II, fig. 2.) 
The long basal branches facilitate the early ripening of a uniform 
crop of cotton, but they will not be an advantage under all circum- 
stances ; as, for example, in dry regions Avhere the Aveevil can be held 
in check by open culture. The necessary exposure of the fallen 
squares to the full sunlight on hot, dry soil would be interfered Avith 
by a plant of low spreading habit and dense foliage. 

EAKLY KEJIX'TION OF SUPERFLUOUS SQUARES. 

That the Kekchi cotton has a limited or determinate growth and 
does not take advantage of the perpetual summer to become a tree or 
even a large bush is evident from the fact that in the latter part of 



EARLY REJECTION OF SUPERFLUOUS SQUARES. 21 

the season most ol' llic flower hiuls and leal" biiils blast and fall oil' 
wliHe still \-ery yoiiii<i-, before the weevil would give attention to them. 
By the time the first of the cotton is beginnini!; to ri])en, most of the 
plants have ceased flowering" and no new leaves are being put forth, 
(lenerally there are bolls only near the base of the i)lant. 

It is a normal character of the cotton plant that the fruiting 
branches shall produce a bud at each node or joint ; that is, at the base 
of each leaf. If all these buds whereto be retained and treated impar- 
tially to the food nuiterials which the plant is able to supply, the 
result would undoubtedly l)e disastrous, since the plant would be able 
to bring very few of its fruits to maturity, perhaps none at all, unless 
a part of the burden were removed by the weevils or by other outside 
causes." It is under the necessity of throwing oil' a part of its load of 
fruit at one stage oi- another of its development, the younger the 
better. 

The rejection is accomplished by the formation at the base of the 
peduncle, or fruit stalk, of special layers of cells of soft texture, 
which soon disintegrate and allow the hud or young fruit to fall off. 
This is one of the man}' instances of the prodigality^ of nature, which 
makes so many allowances in advance for the accidents which beset 
the existence of all living things. The waste of buds is, perhaps, not 
so large in proportion among the perennial " ti'ee " cottons, which 
form a considerable shrub l)efore beginning to blossom. In cultiva- 
tion, however, the tendency has always been to encourage early bear- 
ing, and thus reduce the early vegetative period of the plant and 
bring it to a precocious maturity. The result is that fruiting branches 
are produced, even on young plants, and buds are formed out of all 
true proportion to the actual productive power. 

The habit of rejecting a large part of the squares and bolls is espe- 
cially obvious in the " cluster cottons,'" varieties in which the branches 
are al)normally shortened, so that the leaf surface of the plant is still 
further i-educed. This cuts down still more the j^roductive power of 
the individual i)lant, though there may be a gain in the number which 
can be grown on a given area. 

But cluster cottons have not learned to moderate their promises to 
correspond with their jiowers of performance, and continue to set 
vast numbers of buds, flowers, and bolls, which they are unable to 
ripen. The same is true to a less obvious extent of all our Upland 
varieties, but until the advent of the boll weevil the superfluous buds 
were not a serious factor, and the waste under favorable conditions 
was often well compensated by the power to recover and set a new 



rt 111 Texas it is believed that rain at the time of flowering reduces the crop to 
hiilf the normal quantity, or even less. The explanation given is that water 
settles in the flowers and prevents fertilization. This might serve as an addi- 
tional indication that cotton originated in a dry climate. 



22 WEEVTL-RESISTTNa ADAPTATIONS OP COTTON. 

cfop when in iinfavomblc seasons tho earlier buds were lost, oi* when, as 
occasionally happened in southern Texas, there was a liberal top croj), 
or second period of bearing, late in the autumn months. 

The presence of the weevil alters all these factors. The superfluous 
buds become positively detrimental, for they furnish the breeding 
grounds for successive generations of weevils and enable the pest to 
attain in the latter half of the season such numbers that a top crop 
jiot only becomes utterly impossible, but a menace is prej^ared for the 
cotton of the folloAving year. For, although only a small proportion 
of the weevils live through the w^inter, the nmnber of survivors un- 
doubtedly has a ver}'^ practical relation to the supply maintained at 
the end of the previous season, and this again is merely a question of 
thi.s persistent production of buds, now nuich worse than useless. 

A short-season variety of cotton having a sufficiently determinate 
habit of groAvth would by itself constitute a solution of the w-eevil 
])roblem. The Department's entomological investigations in Texas 
indicate that it is only the weevils hatched in the last month of the 
grownng season — in October or November — Avhich haA^e a prospect 
of surviving the winter. A cotton which ceased to produce buds 
after July or August would remove the chance of wintering over 
from all the weevils except the few that might develop in the bolls, 
an almost infinitesimal number compared with those that now attain 
]naturity in the squares. Much would be gained, of course, if all 
planters would promptly pick their cotton and then pull up and 
destroy the plants, being especiallv careful to collect the infested 
bolls. But to carry out efficiently such a programme is difficult and 
expensive. 

To what extent, if any, the Kekchi cotton will meet this need of a 
short-season determinate variety, it is too early to form an opinion, 
but the fact that it has these qualities to a higher degree than any of 
the varieties hitherto known in the United States must be accepted 
as evidence, at least, that the possibilities of this method of protection 
have not been realized. In the latter i)art of the season the Kekchi 
cotton ceases the u])ward growth of the main stem and its branches 
and regularly drojjs the greater part of its buds before they are large 
enough to be entered or fed upon by the weevils, and the analogies 
to be drawn from the habits of other plants will justify persistent 
efforts toward the development in this and in other stocks of the 
habit of rejecting the buds still earlier or of not forming them at all 
after the first crop of fruits has set. Many j^lants have, in fact, 
exactly this habit so desirable in cotton ; they continue to flower until 
jiermitted to set seed. 



SEASONAL BEARING OF PERENNIAL VARIETIES. 23 

SEASONAL BEARING OF PERENNIAL VARIETIES. 

The continued existence of perennial cottons in weevil-infested 
countries, like Giiateniala, proves the presence in these also of means 
of protection. One of the most important is, doubtless, the produc- 
tion of an annual crop at a definite season, leaving the weevils with- 
out opportunity to breed in the intervening months, thus greatly 
reducing their numbers. 

The popular impression that tropical plants take advantage of the 
continuous summer climate and blossom continuously is correct only 
for a snuill minority. Where there are definite Avet and dry seasons 
many tropical plants have alternating, periods of groAvth and rest 
iilmost as pronounced as in temperate climates, and even in regions 
of continuous humidity there aiv some s])ecies wliich shed their leaves 
annually and rest for a time. 

A further general i-eason for a simultaneous annual blossoming of 
all the flowers of a species is undoubtedly to be found in the greatly 
increased opportunities of cross-fertilization, just as many insects 
Kwarm and many birds and mammals collect in flocks before the 
breeding season. Simultaneous flowering is carried to a remarkable 
extreme among the bamboos, where whole species grow for long series 
of years without flowering, and then flower and die at once over long 
distances and in spite of local diversity of conditions which might be 
expected to advance or retard maturity. 

Accordingly, while it would not be reasonable to insivSt that peren- 
nial varieties of cotton have adopted the habit of annual flowering 
only because of the boll weevil, the analogy of other plants may be 
invoked to show that such a character can be brought about by select- 
ive influence. The weevil could certainly assist in the development 
of such a tendenc3% especiall}^ if there were a season of the year in 
which the insects were less numerous, from climatic or other external 
causes as yet unknown. 

The tropical varieties of cotton are, as is well knoAvn, mostly peren- 
nial, and some of them develoj:) into trees of considerable size, the 
trunk attaining a diameter of or 8 inches, and the main branches a 
length of 15 or 20 feet. The existence in Mexico of tree cotton 
immune to the weevils has been reported, but as yet this has not been 
substantiated. Possibly the weevil has not yet penetrated some of the 
remote and arid parts of the republic. In eastern Guatemala, at 
least, the tree cottons appear to enjoy no immunity from the weevil, 
and at the time of the visit of the writer it was often impossible 
to secure uninjured bolls, even as samples of the varieties. The 
native cottons of the island of Cuba, according to Mr. E. A. Schwarz, 
also have the habit of annual blossoming, in the intervals of which 
the number of the weevils becomes greatly reduced. The cutting back 



24 WEEVIL-RESTRTTNG ADAPTATIONS OF COTTON. 

of the cotton by the Indians a( Ivubinal, as described in the next 
paragraph, is an artificial means of attaining the same end, but the 
native Sea Ishmd cotton, found at San Lucas, and the Kidney cotton, 
at Tucuru, are the best (xuatemalan e\anij)h>s of this j)rotective habit. 

ANNUAL CUTTIN(; BACK OF TEKENNIAL VARIETIES. 

T^liile the annual variety of cotton protected by the keleps is the 
basis of the only held culture found in eastern Guatemala, the Indian 
population of the central plateau about Salama and Rabinal raise 
small (juantities of cotton in their dooryards by means of another 
cultural expedient, apparently of great antiquity, as indicated by the 
extent to which the plant is adapted to the cultural conditions. The 
variety is perennial and has very small and inactive nectaries, pos- 
sibly as an adaptive result of the dryness of the climate. 

Most of the perennial varieties begin bearing only after the plants 
have attained considerable size, but the Ral)inal cotton is a notable 
exception to this rule and avoids injury from weevils by the very 
prompt flowering and fruiting of the new^ shoots. 

The weevils are present in numbers, and are frequently seen crawl- 
ing about on the plants in a leisurely manner quite different from 
that which they affect in regions stocked Avith keleps. At the time 
of our visit not a single boll or bud of any except the smallest size 
could be found which had not been attacked by them. Nevertheless, 
a crop of cotton is secured at another season. In the month of April 
the Indians cut back all the bushes to the ground, and as the cotton 
is always planted immediately about the doors of their houses, where 
the chickens and turkeys congregate, the mortality of Aveevils at this 
time is probably very great. The protection of the domestic birds 
doubtless continues until the new shoots have grown out of reach. 

As soon as the plants are a few inches high they begin flowering, 
and l)efore the Aveevils are sufficiently increased in numbers to become 
injurious a crop has been set. FloAAcrs and fruit are commonly borne 
on the lower branches, only 6 or 8 inches from the ground. The 
Indians say that if the cotton is not cut back, but allowed to grow 
tall, they get no crop. The fact is that by that time the weevils are 
too numerous to permit normal bolls to be formed. Our search for 
such was quite in vain on both our visits to Rabinal. One boll which 
gave no certain external proof of injury was wrapped up in a paper 
and retained as a sample, but was overlooked in packing and not 
transferred to the preserving fluid. When the paper was unwrapped 
a few weeks later three dead boll Aveevils were found. 

The Rabinal cotton crop is evidently not large, but the harvest is 
said to be regular, and the area of fertile land in this district is so 
small that none of it is wasted. Much foreign thread is now 



HAIRY STALKS AND LEAF STEMS. 25 

imported, however, for \veavin<^ in the native h)<)iiis. The industry 
has greatly declined in the last century, perhaps because chickens 
have been generally substituted for turkeys, which were formerly the 
only domestic fowl possessed by the Indians. 

All attempts at establishing field cultures of cotton in this region 
have failed. The local public, which does not take the weevil factor 
into consideration, is firmly persuaded that cotton will not bear ex- 
cept in the heavy, rich soil of the dooryards of the Indian villages. 

irAIUV STALKS AXD LEAF STEMS. 

The weevil on foot is a rather slow-moving, clumsy insect, and it 
has been ascertained in the course of the investigations conducted by 
Messrs. Hunter and Hinds that its movements on the plants are to a 
great extent impeded by luiiry stalks and leaf stems. The smooth 
Egyptian and Sea Island varieties were found to be more susceptible 
to Aveevil injuries than the hairy Upland sorts. The Kekchi cotton 
is still more hairy, however, than the United States varieties, and 
gains an added advantage from this fact." The longer it takes the 
weevils to climb from one biul to another the greater are the chances 
of their being caught by the keleps. The latter insects, owing to 
their nnich longer legs and the claws with which their feet are armed, 
are not only able to travel readily over the hairs, but find them of 
definite assistance. On smooth surfaces they are much less adroit 
in catching and stinging the boll weevils. In our experiments, too, 
they seemed to prefer the hairy I'pland cottons to the smooth Sea 
Island varieties. 

The difference between the two insects in this respect may also be 
illustrated by the fact that the keleps are unable to ascend a ])erpen- 
dicular siu'face of clean glass, a feat which the weevils accomplish 
without difficulty. 

That the Guatemalan cotton was more attractive to the keleps than 
the United States Upland and Sea Island varieties planted in ad- 
jacent roAvs seems to be indicated by a census of our plot experiment, 
taken April 19 by Mr. Argyle McLachlan. Kelep nests were 
found at the bases of 41 per cent of the plants of the other varieties, 

a Though distinctly hairier than our ordinary Uph^nd varieties, the Kekchi 
cotton is exceeded in tliis respect by two other Guatemalan types, as well shown 
in a field tfst at Lauhani. Md. The Pachon cotton obtained by Mr. William R. 
Maxon in the Retalhuleu district of western Guatemala is distinctly more 
hairy than the Kekchi variety, though it seems to be lacking in other weevil- 
resisting features. The iiivolucral bracts are not closed any more than in the 
Sea Island or Egyptian types. The most hairy cotton of all is the Rabinal 
variety, at least in the form it has taken at Lanham. The plants are very much 
more robust in eveiy respect than at home in Guatemala, and the hairy covering 
shares in this increased vigor. 



26 WEKVTL-RESTSTINCr ADAPTATIONS OF COTTON. 

while 7(5 per ceii^ of the phiiits of the Kekchi cotton were faA'ored with 
kelep nests. This apparent preference may be somewhat exaggerated, 
j)erhaps, in view of the fact that the phuits were often farther apart 
in the rows of the Kekchi cotton, the seed having germinated very 
irregularly. Moreover, the superior attraction of the Kekchi cotton 
for the keleps may not have consisted entirely in the greater hairiness 
or the more abundant nectar. The compact foliage and spreading 
lower branches of the Kekchi cotton give greater protection from the 
midday sun, which the keleps utilize by greater activity in the middle 
of the day. 

With the Sea Island varieties it seemed obvious, however, that the 
smooth stems, more open liabit, and smaller supph' of nectar result in 
distinctly less attention from the keleps. From or 10 o'clock on hot 
days the}^ foraged very little, and seemed to have quite disappeared 
from these varieties, though still to be found in considerable numbers 
on the stems of the Upland varieties and most of all on the Kekchi 
cotton, which appears especially adapted for the coriifort and con- 
venience of the keleps. 

It was noticed, how ever, that the keleps Avent much more often into 
the involucres of the Sea Island and Egyptian varieties than into those 
of the Kekchi cotton, for the simple reason, probably, that they can 
get in more easily. 

In the latter part of the season, after the weevils had gained a foot- 
ing in this field. Professor Pittier noticed a very decided preference 
on their part for the Egyptian varieties, though it seems certain that 
this type of cotton had never been planted in the country before. The 
])artiality of the w^eevils might be explained, perhaps, on such grounds 
as the relative absence of the keleps, and also the ease of access to the 
buds of the Egyptian cotton allowed by the more open involucres. 
However, a slight change of food or of conditions of growth is often 
a distinct advantage to plants and animals, so that a direct preference 
for a new^ variety as food might reasonably be expected, and similar 
instances are known. 

The greater hairiness of the stems and the presence of the keleps 
may also explain why the weevils in Guatemala were seldom seen 
walking about on the cotton plants as they do in Texas. On the 
other hand, they take to wing very readily and seem to prefer to 
alight in the open flow^ers, the only places on the cotton plants where 
they are safe from the keleps. 

The petals are so smooth that the keleps seldom descend into the 
flowers, and when they do sometimes appear to be unable to climb 
out. The petals of the Sea Island sorts are smooth even on the mar- 
gins, sometimes entirely so, while those of the Upland varieties are 
fringed with fine hairs w'ell up on the sides, if not all the w^ay round 
the apex. 



PENDENT BOLLS. 27 

The liiil)ilily 1<» caijliirc by such an insect as the kelep may also 
aiford an explanation of the peculiar sedentary habits of the male 
weevils, which often remain stationary in one involucre for long; 
periods, or as long as their food snpply lasts. It is necessar}^ for the 
females to go about in search of fresh squares for egg laying, but 
similarly active habits on the part of the males would subject them 
to nnnecessary danger. 

PENDENT BOLLS. 

The early bearing of the Kekchi cotton is made possible, as already 
noted, by the nnusual devel()i)ment of the lower lateral brandies, 
which often have a drooping habit, leaving the buds and bolls in 
pendent position, intead of upright. There are several advantages 
in this arrangement, one being that the instinct of the weevils leads 
them to the upper portion of the plant. In a very badly infested 
field without kelep protection, the only bolls which escaped the 
weevils were a few lying close to the ground on these lower pendent 
branches of the Kekchi cotton. Only at the time of flowering does 
the peduncle curve upward and give the flower its normal upright 
position. Thus these drooping lateral branches of the cotton, which 
seem to hide the buds and bolls away from the weevil, may be looked 
upon as a short step in the direction of such })henomena as the 
cleistogamous flowers of violets which i-emain buried in the ground, 
or those of the peanut which, after flowering, burroAV into the soil to 
ripen their seeds. 

The flowers of the cotton plant open in a more or less directly up- 
right position, and this is retained by the boll in most varieties. In 
the so-called " stormproof " sorts, however, the bolls hang down, and 
this is looked upon by many i^lanters as a distinct advantage, since 
when the boll is ri^Dii' and oj^en the rain does not beat into it and wet 
the cotton or wash it out, but is shed by the protecting outer shell and 
involucre. 

On pendent bolls the external nectaries are brought upward, so 
that there is no danger of an abundant secretion of nectar being lost 
by dropping off. The surface of the nectary is papillate and has a 
somewhat Avaxy appearance. 'Jlie secretion often collects as a dis- 
tinct drop. The nectaries are also more readily visited by the keleps, 
and the young bolls are likely to be better protected by them. If 
these remained upright, the weevils would be more likely to alight 
and enter the involucre at once. 

The drooping habit may have a mechanical explanation as the re- 
sult of the weakness of the comparatively slender lateral branches. 
It is also to be connected, perhaps, with the habit of early flowering 
and fruiting, since this would bring heavier bolls upon smaller and 
softer branches which would be twisted over by their weight. In 



28 weevil-kf:ststtng adaptations of cotton. 

(lie ]:i((M- niul more iipriiilit varieties tho flowoi-s are not formed until 
the wood of the branches has hardened and become strono- and rigid. 
Pendent bolls may thus be said to l)e incompatible with the cluster 
habit, which is brought about by the abnormal shortening and thick- 
ening of the'lateral branches, which are al)le to hold theii- flowers and 
fruits rigidly upright, except as they may be turned sidewise by being 
crowded together. The cluster cottons, too. have the undesirable 
tendency to an abnormal multiplication of squares and young bolls, 
many more than the restricted leaf surface of the plant will enable 
it to ripen. This superabundance of flowers and fruits gives, how- 
ever, the greater encouragement to the weevil, and uses up vegetative 
energy which could be better employed in the prompt ripening of the 
bolls already set. It is no unconnnon thing, however, for even half- 
sized bolls of cluster cottons to die without any sign of external 
injury or disease, while other varieties close by remain perfectly 
healthy. The cause is probably to be found in inadequate nutrition, 
but this might also be expected to give them increased susceptibility 
to injury from parasitic enemies of every kind. 

It is not unlikely, too, that the drooping habit may be connected 
with the greater size of the inside nectaries of the Guatemalan vari- 
ety. These are, as far as we have seen, larger than in any other 
American variety yet known ; but the Asiatic cottons, which have the 
inside nectaries still larger and more active, are also more definitely 
pendent. The involucre is grown together at the base, as though to 
more thoroughly protect the nectaries from above — from the sun, 
which would dry up the secretion, and from the rain, which would 
wash it off. 

The nectar is formed in great abundance, and Mr. F. J. Tyler, of 
this Department, has called attention to the fact that the surface of 
the nectaries of the Asiatic cottons, instead of being merely papil- 
late, as in the American Upland varieties, has a coA'ering of close- 
standing fine hairs, to which its velvety appearance is due. 

Finally, it may be remarked that for cotton with upright bolls the 
inside nectaries are often an element of danger, since when the secre- 
tion is abundant and is not removed it flows along the bases of the 
involucre and may serve as a medium for the germination of parasitic 
fungi or bacteria. Bolls are not infrequently found diseased arou.nd 
the base, apparently from this cause. 

EXTRAFLORAL NECTARIES. 

The cotton plant is not without fl(jral nectaries similar to those of 
related genera, consisting of fringes of nectar-secreting hairs lining 
the pits inclosed between the bases of the petals. The nectar serves, 
doubtless, the same purpose as in other plants, the attraction of the 



KXTRAFLOKAL NliCTAKIES, 29 

lioney-loviiig insects tlu'(>ii<i::h which cross-fertili/atioii is secured. 
It does not appear, however, that the flora] nectaries of the cotton 
have any connection witli the problem of Aveevil resistance, although 
the weevils seem in (iuatemala to spend a considerable part of their 
time in the flowers, which are indeed the only safe places for them 
on plants protected by the keleps. It had been noticed from the first 
that the keleps seldom visit the cotton floAvers, and Mr. Kinsler has 
learned a very adequate explanation of this fact, namely, that they 
are able to climl) out of the flowers only with considerable difficulty, 
and sometimes remain iniprisoned in spite of all their efforts to 
escape. 

The functions of tlie extrafloral nectaries of })lants are, as far as 
can l)e ascertained, similar to those of the floral nectaries to the extent 
that they attract insects, but beyond this there is a fundamental dif- 
ference; the floral nectaries and higlil}^ colored floral organs serve to 
secure visits of flying insects and thus maintain intercommunication 
and cross-fertilization between the different members of the same 
species, in spite of the fact that the individual plants are rooted fast 
in the ground. The extrafloral nectaries, on the other hand, attract 
to the plants insects which will remain upon them as ]>ermanent resi- 
dents, and this is the end secured by the extrafloral nectaries of the 
cotton. 

It may be objected by some that no use or benefit to the plant has 
been ascertained in the case of many species which have extrafloral 
nectaries and other insect-attracting devices. Much remains to be 
learned concerning these marvelous biological sjiecializations, and 
there are two obvious alternatives which need to be canvassed before 
belief in the adaptive nature of extrafloral nectaries and analogous 
structures can be destroyed. The character and extent of many such 
specializations show that they have existed for a long time. They 
may have served protective purposes no longer apparent. The other 
consideration is that some of the symbiotic sj^ecializations existing 
between such plants as Cecropia and Acacia and their insect inhab- 
itants have arisen through selective encouragement, nnich as the 
special characters of our domestic i)lants and animals have been 
developed. It may be sufficient, in other words, that the nectaries or 
other structures be of use to the insects which have done the selecting. 
It ma}' seem absurd to think of bushes or trees as having been domesti- 
cated by ants many thousands of years ago, but the wonder is no 
greater than that ants and termites regularly maintained subter- 
ranean fungus gardens ages before mushroom culture was undertaken 
by man. 



80 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

NECTARIES Oi THE LEAVES. 

The midrib of each leaf bears on the under side an oblong: pit, 
from which a drop of nectar may often be seen to exude. Tliis is 
collected and eaten by the keleps, which are thus induced to visit 
all parts of the plants, especially while they are still small. 

The habit of collecting the nectar was not previously known to 
exist among the insects of the family (Poneridse) to which the kelep 
has been referred. Nevertheless, the fact is not open to question. 
The process is easy of observation in even greater detail than Avith 
the true ants or the bees, because the keleps do not, like these insects, 
have the art of regurgitating their food. They merely lap the nectar 
up to form a drop, which, protected by the widely ()j)ened mandibles, 
is carried into the nest to feed the queen and the young. 

Nectaries, or at least nectary-like depressions, are to })e found 
probably on the leaves of all vai'ieties of cotton, though very small 
and apparently inactive on some of the larger tree sorts." The 
shape of the nectaries also vai'ies greatly in the ditfei'ent sj^ecies and 
varieties, some being longitudinal, others transvei'se, and still others 
crescentic or even sagittate. Some varieties have nectaries on the 
three principal veins, and some even on five veins. 

The leaf nectaries of the Kekchi cotton are to l)e found on the 
midrib of the leaf about 1.5 cm. from the base. They consist of a 
rather shallow longitudinally oval depression surrounded by a broad 
raised rim. The midrib often appears distinctly narrower above the 
depression than below it, as though there were extra tissues to supply 
it. The secretion is quite active, nearly all the nectaries shoAving a 
small amount of liquid, which sometimes spreads out on the adjacent 
surfaces. 

These nectaries furnish, as might be expected, a medium favorable 
for the growth of molds or fungi, and there is often a considerable 
network of dark-colored fungus mycelium creeping in and about the 
moistened depressions, and with occasional erect, needlelike points, 
which may be fruiting bodies. 

« This was not true, however, of a Mexican " tree cotton " of the Upland 
type grown in the Department's experimental plots in Texas last year. Large 
nectaries were generally present on three veins of each leaf, and the midvein 
often had two. They were of the crescentic or sagittate type, bnt often 
extremel:' long and distorted. Another Mexican tree cotton, with a different 
type of lighter green foliage, suggesting that of Bixa, had nectaries only 
on the midvein and these reduced to a narrow groove?. The vein was not 
thickened nor the niiirgins raised. Tlie two vai-ieties were about as different 
as could well he with resi>e(t to nectaries. Neither produced either flowers 
or fruit, so that their true relationshii)s were not to be ascertained. 



NECTARIES OF THE INVOLUCRE. 31 

EXTERNAL NECTARIES OF THE INVOLUCRE. 

The Guatemnlaii cotton protected by the keleps has three broadly 
oval or reniform pits at the base of the involucre, one at the middle 
of the base of each of the involucral leaves." These are larger, dee])er, 
and more active than the nectaries of any of the Texas varieties as 
yet observed, though there is very great diversity of size and nectar- 
secreting activity. In some of the varieties these nectaries are 
reduced to mere rudiments or are entirely wanting. The depres- 
sion may be present, but with no secreting tissue. The variety nearest 
approaching the Guateuuilan cotton in having large and active necta- 
ries is the Redshank, but the King and other related sorts also have 
fairly large nectaries. 

The drooping or pendent i)osition of the bolls in the Kekchi cotton 
may be correlated with the special development of these nectaries, as 
already noted. In the middle of the day the keleps are not vei*y 
active, but the nectaries are sometimes full to overflowing. If the 
bolls kept the erect position usual in the varieties cultivated in the 
(Jnited States the nectar would frequently dro}) off and Iw lost, but 
when the fruits hang down the cuplike nectaries are brought upper- 
most and hold the liquid much longer. 

The evolutionary origin of these nectaries is fairly obvious. The 
bracts are to be looked upon merely as modified leaves, with nectaries 
which have increased in size and activity as the leaves have become 
smaller and more specialized. 

INNER NECTARIES OF THE INVOLUCRE. 

As though to induce the keleps to come inside the involucre and 
thus more effectually i)rotect the young buds and bolls against the 
Aveevil, the Guatemalan cotton is also provided with unusually large 
interior nectaries, alternating in position with those of the outer 
series and thus placed opposite the edges of the involucral leaves or 
bracts. These inside nectaries, like the outside ones, are larger and 
more active than those on most of the cottons cultivated in the 
Southern States, but the closing of the involucre and the devolopment 
of the inside nectaries have been carried much farther in the Old 
World cottons belonging to the species (ro.s.'^ypk/m lierhacewm. 
Here the external nectaries are quite wanting, but the internal ones 
are enormously larger and heartshaped, and secrete nectar in such 
quantities that it often flows out in the groove between the adnate 

'' Instances are occasionally found wliere only two nectaries are developed, 
but such deficiencies are niucli less tre(inent than in other varieties of the 
Upland and Sea Island series. Tlie Iial)inal cotton counnonly has only two 
external nectaries. The Old World cottons thus far observed have uo nectaries 
in this position. 



32 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

bracts to iiioistcii the ed^es of the iiivohicre. As yet, however, the 
purpose of these achiptatioiis in the Asiatic cottons is entirely 
unknown, both the boll weevil and the kelep being absent in the 
Eastern Hemisphere. 

The botanical homology of the inner nectaries is somewhat different 
from that of the outer. They correspond in all probability with the 
nectaries which are found on the calyx of some of the species of 
Hibiscus, but there the calyx is large and covers the buds and each 
sepal bears a nectary near its middle. 

NECTARIES OF GUATEMALAN SEA ISLAND COTTON. 

A variety of Kidney cotton planted in small (juantities by the 
Indians at Trece Aguas, Guatemala, has the outer nectaries very 
variable in size and commonly ((uite wanting." The inside necta- 
ries seem always to be developed and are unusually large, l)eing ex- 
ceeded, as far as known, only l)y those of the Asiatic varieties. The 
nectar secretion is' also very abundant. No weevils were found upon 
this cotton, nor any keleps. 

On the other hand, the free-seeded Sea Island cotton found by 
Mr. Kinsler in the San Lucas '' neighborhood, not far from the 
kelep cotton culture of Secanquim, reverses again the tendency of the 
Kidney cotton to the great development of the inner nectaries and 
the suppression of the outer. The latter are, in the San Lucas cotton, 
nearly alwaj^s present, of rather large size, and of a red color. The 
inner nectaries are often rudimentary or quite absent. 

CONTINUED SECRETION OF NECTAR. 

Our Upland varieties commonly secrete nectar only at the time of 
flowering, but in the Kekchi cotton the liquid continues to exude 
until the boll is nearly or quite full grown, thus securing the protec- 



a This variety not infrequently produces flowers with only two bracts, closely 
appressed, like a clam shell. In one such instance there were two nectaries at the 
base of each bract, or, to be more exact, two separate nectaries on one side and 
one partly divided nectary on the other, as though the nectary belonging to the 
deficient third bract had separated into two ])arts and joined the other necta- 
ries. 

^ This San Lucas Sea Island cotton is probal)ly the variety in which the 
weevils were found alaindant in 1902, when the first intimation was gained 
that the Kelvchi cotton had means of protection against the weevil. The San 
Lucas cotton is attaclced not only by weevils, but by another long-bodied in- 
sect larva, evidently lepidopterous, that gnaws through the boll at the ends, 
both from above and below, and eats out the seeds. Nothing of the sort has 
been seen in the fields protected by the keleps. There was also noticed in this 
cotton an occasional abnormality closely comparable to the navel orange. 
Rudimentary parts like a small secondary boll were found in the middle of 
bolls otherwise normal. The orange tree and the cotton plant belong, it may 
be remembered, to related families. 



BRACTLETS SUBTENDING INNER NECTARIES. 33 

lion of the keleps for a longer period. The temporary character of 
the secretion in our United States sorts Avas reported by Professor 
I'release several years ago. 

In Guatemala, however, the young bolls seem to be quite as effi- 
cient as the flowers. It is even possible that this generosity on the 
part of the plant is excessive, since if the number of keleps is small 
they may find all the nectar they need on the lower bolls, and hence 
have less inducement to inspect other parts of the plant. Under 
favorable conditions in Texas the cotton plant produces a much 
larger number of flowers than in Guatemala, so that what is lacking 
in quantity may be made up by numbers, in case it should become 
possible to utilize the keleps in Texas. 

RACTLETS SUBTENDING INNER NECTARIP:S. 

The Kekchi cotton is distinguished from all our Upland and Sea 
Island types by the more regular presence and nnich larger size of 
a series of bractlets. a pair of Avhich usually subtends each of the 
inner nectaries. In other varieties these are either wanting entirely 
or are rare and rudimentary.* The bractlets are inserted somewhat 
obliquely, with their margins in contact below the nectary. 

Sometimes they serve to conduct nectar to the edge of the involucral 
bracts, the nectar following along between the slender bractlets like 
ink between the nibs of a pen, as though to coax the keleps inside the 
involucre. This must happen rather infrequently, however, to judge 
from the great irregularity in the size of the bractlets. Sometimes 
they are half an inch or more long, and extend well into the angles of 
the involucre, or even project outside. (PI. III.) Nevertheless, it 



« Professor Trelease, who studied the American Upland varieties, ai)i)ears not 
to have found the bractlets in pairs. He says: "These glands (the inner nec- 
taries) belong in reality to an inner whorl of three bracts, alternating with 
the outer ones, but generally wanting. In stunted plants, especially as cold 
weather comes on, one or more of these inner bracts may be found." (See 
Comstock. 1875, Report upon Cotton Insects. .324.) 

The shape and position of the bractlets seem to warrant the suggestion tliat 
they represent the stipules of the outer bracts instead of an independent inner 
whorl of bract leaves which luis first become specialized and then become rudi- 
mentary. The suggestion has the further warrant in that it may help to explain 
the numerous involucral appendages of some of the related plants, which range 
about the number 9 — that is, 3 leaves and 6 stipules. The normal number should 
be 6, if the two whorls of leaves were represented. One of the Guatemalan 
species of Hibiscus examined with this interpretation in mind seemed to con- 
firm it by showing very often .3 of the appendages broader than the others, 
though the total number varied from 8 to 11, with an irregularity quite compar- 
able to that of the bractlets of the cotton. Even the bracts of the cotton some- 
times vary, involucres of 2 bracts being found occasionally, and in rare 
instances 4. 

9962— No. 88—05 M 3 



34 WEEVIL-KESISTING ADAPTATIU^'S UJb' CUTTOJS. 

may Avell be (juestioned Avhether these inner bracllets have remained 
unusually large in the Kekchi cotton because they have a definite 
function or because of tlie greater size and activity of the adjacent 
nectaries. 

A variety of cotton called Pachon. planted rather extensively in the 
Retalhuleu district of western Guatemala, and likeAvise protected by 
the keleps, is similar to the Kekchi cotton in many respects, including 
the possession of these large stipular bracts subtending the inner 
nectaries, but with the addition that the bracts are fringed with long 
hairs, as though to hold the nectar the better. This may also be the 
function of the hairs which cover the nectaries of the Old World 
cottons 

EFFICIENCY OF THE KELEP PROTECTION. 

The special development of the extrafloral nectaries in the Kekchi 
cotton has been noted in former reports, it being the nectaries wdiich 
attract the keleps to the cotton plant. That the kelep preys upon boll 
weevils and protects the cotton crop was learned last year, but it was 
still possible to question the practical value of this form of defense. 
Such doubts would not have survived an inspection of our recent 
experiments in Guatemala. A small field of cotton just outside the 
kelep area was attacked by the weevils in such numbers that not a 
single normal boll developed on any of the United States Upland and 
Sea Island varieties. In the field protected by the keleps the weevils 
obtained no footing until the plants were well grown and an excellent 
crop of full-sized bolls had been developed. 

To test the efficiency of the keleps as destroyers of boll weevils and 
as protectors of cotton Would be possible in Texas only by stocking a 
large area with keleps — a difficult and expensive undertaking. No 
small tract would give a fair indication, since the weevils from the 
whole neighborhood would continue to come in, and, although they 
might soon be captured, would be able to do vastly more damage than 
would be possible if the whole region were stocked with keleps. 

In Guatemala, however, it was quite possible to contrast a protected 
with an unprotected piece of cotton by the simple exj^edient of plant- 
ing outside the area occupied by the keleps. A more striking result 
could hardly be imagined. For several weeks, during wdiich the two 
plots w^ere under continuous observation, the one remained almost 
entirely free from weevils and Aveevil injuries and set an excellent 
crop. Avhile in the other scarcely a flower opened or a boll developed. 
The very few exceptions were on the concealed drooping branches of 
the native Kekchi cotton. 

The weevils became, indeed, too numerous for their own prosperity 
and fed upon and destroyed the very young buds before they were 
old enough to breed larvae. Twenty-five fallen squares collected and 



EFFICIENCY OF THE KELEP PROTECTION. 35 

examined from under the plants of the plot without keleps yielded 
only 6 larvae, or 24 per cent. They even attacked the young leaf 
buds, as observed last year at Rabinal. 

A large proportion of the injuries were caused by feeding punc- 
tures, but this only emphasizes the fact that the number of weevils 
which migrated into this plot Avas sufficient for a complete destruc- 
tion of the crop, and since the other experiment protected by the 
keleps was much nearer to the fields of the Indians there is every 
probability that the weevils would have been, if possible, even more 
numerous if the keleps had not been at hand to catch them. 

The unprotected plot Avas located at about one-quarter of a mile 
outside of the belt of Indian cotton culture, on land not inhabited by 
keleps. The weevils lost no time in finding the new field. Infesta- 
tion was complete, and quite as destructive as in Texas, the Aveevils 
being so numerous as to OA^ercome AvhatcA^er resistance the cotton 
might liaA^e been able to oppose to smaller numbers of the pests. 
The Sea Island, Egyptian, and United States Upland varieties A\'ere 
not permitted to produce floAvers or eA^en full-sized buds, and even 
the natiA'e Guatemalan varieties shed their squares before the per- 
sistent onslaughts of the Aveevils. 

Cotton is regularly cultiA^ated by the Indians in this immediate 
neighborhood, and Indian plantings more or less infested Avith 
weevils Avere to be found within short distances of the protected field. 
Nevertheless, the keleps proA^ed to be sufficiently abundant on this 
piece of ground to completely exclude the AveeAdls. There Avere 
enough, indeed, to protect Avith apparent impartiality all the kinds 
■ of cotton included in the experiment, but if the numbers had been 
less and the plants had been closer together, as in the Indian fields, 
Ave may be sure that those producing the most nectar Avould haA'e 
recei\^ed the most protection from the keleps. 

The Aveevils Avere seldom to be found in the plot stocked Avith 
keleps as long as the Indian cotton remained in Adgorous groAving 
condition, but about the time the Indian cotton ripened, the weevils 
seemed to make a more determined raid on our field, and along one 
side nearly cATry plant suffered somcAvhat, though the weevils 
could rarely be found except in the open floAvers, Avhich seem 
to be recognized as their only safe roosting places. In a A\^eek or 
ten days there Avas a distinct falling off, so that A^ery little damage 
Avas being done, and there Avas another short interA^al of practically 
complete protection. But after this a reneAved onslaught began and 
the • numbers of AvecAals gradually increased, the Upland and Sea 
Island plants continuing to produce thousands of ncAv squares in 
Avhich the weevils Avere able to breed, quite as in the United States. 

That the keleps are definitely attracted to the cotton plants, as 
stated in previous reports, is fully demonstrated by the fact that 



36 . WEEVIL-KESISTING ADAPTATIONS OF COTTON. 

liiaiiy of the colonies iiio\'ed their nests to new buiTows excavated 
immediately at the bases of the cotton plants. In some parts of the 
field the proportion of cotton plants having kelep nests established 
about their roots reached nearly 75 per cent, whereas the chance 
that the positions of the cotton plants which stood in regular rows 
would coincide with those of kelep nests would not be one in hun- 
dreds. 

The success of this experiment would seem to justify fully the 
suggestions made in connection with the first announcement of the 
discovery of weevil-resisting adaptations of the cotton plant, namely, 
that the protection which these Central American varieties had 
been able to Secure from the kelep had afforded them an opportimity, 
perhaps unique, of developing other resisting adaptations. The 
Kekchi and other related cottons, though having no monopoly of 
weevil-resisting characters, furnish, however, the only instance as 
yet known to scientific observation in which a field culture of cotton 
has been maintained for long periods of time under climatic condi- 
tions favorable to the boll weevil. 

In Central America, at least, the secretion of nectar by the cottori 
is not a useless or meaningless function, as observers of the plant in 
other parts of the world have sometimes supposed. The cotton is 
not the only plant upon which the kelep can live, nor the boll Aveevil 
the only insect upon which it preys. To secure the attention and 
obvious preference of the kele]) tlie cotton has been obliged to put 
forth the superior attractions provided by its numerous extra floral 
nectaries. 

This additional proof of the \'alue and efficiency of the kelep does 
not affect, of course, the possibility of acclimatizing it in the United 
States. A more extended search in Guatemala resulted in finding the 
insects under a wide range of conditions, and at altitudes of from "200 
to 2,000 feet. It lives and thrives, moreover, in soils very nuicii drier 
than those to which it was supposed last year to be confined. Last 
year's experiments in Texas indicated likewise that the kelep with- 
stands drought much better than it does standing water in its barrows, 
and care is being taken this season to locate colonies with a view to 
adequate .drainage. 

OTHER NECTAR-BEARING PLANTS VISITED BY THE KELEPS. 

The honey-collecting habits of the keleps are not confined to the 
cotton. Another favorite is a si3ecies of Bidens {B. pUosa) called by 
the Indians '' tshubai," which has considerable value as a forage 
plant, being of quick grow^th and succulent texture. 

The preference of the kelep for the tshubai as a second choice after 
cotton w-as noted last year, but no explanation was found, though 



THE INVOLUCRE AS A PROTECTIVE STRUCTURE. 37 

the plant was searched foi nectaries. It was noticed by Mr. Kinsler 
that the keleps seemed to be giving especial attention to the midrib 
near its jmiction with the veins of the lower divisions of the leaf. 
Our lenses then revealed the fact that there are two minute raised 
Avings or margins running along the upper side of the midrib and 
petiole, forming two narrow grooves in which the nectar is evidenth^ 
secreted. The grooves are also protected by a row of fine hairs Avhich 
project across them from the raised margin. The behavior of the 
kelep thus receives a practical explanation, and the tshubai finds a 
)-egular place next to the cotton among the plants protected by tjie 
kelep. The nectar-secreting habit of the tshubai nuiy also explain 
its being eaten so readily l)y stock, and may help to give it standing 
as a forage plant, in spite of its weedy and unpopular relatives. 

A second member of the composite family often visited b}^ the 
keleps is the '' sajal," a species of Melanthera (probably M. deltoklea) , 
which also has local value as a forage plant, being eaten greedily 
by horses and inules, even in preference to grass. No nectaries have 
been found on this, A third composite, not A^et identified, produces 
nectar in small depressions at the base of the leaf on the under side. 

THE INVOLUCRE AS A PROTECTIVE STRUCTURE. 

Cotton is the only plant known to be attacked by the boll weevil, 
and it is also unicpie among its relatives in the possession of a large 
leafy involucre. This may be a mere coincidence, or it may be that 
the weevil has had a considerable influence in the development of the 
involucre, depending iii)on the antiquity (»f the contact between the 
insect and its host })lant. The involucre has, it is true, functions 
other than the exclusion of the weevils, since it takes the place of the 
calyx in protecting the young bud. but the reduction of the calyx 
probably followed the enlargement of the bi'acts, instead of preceding 
it. But however originated, the large Ijracts have, at the present 
time, a definite value in the j)rol)lem of weevil resistance. There are 
several specialized chai-acters which appear as though definitely cal- 
culated to increase the efficiency of the involucre in excluding the 
weevils from the young buds. 

INVOIJTCHAL lUiACTS (JROWN TOGETHER. 

Both the Kekchi and lAal)inal cottons frequently have the involucre 
closed at the base, the three bracts being grown together, thus making 
it impossible for the weevils to enter from below. In the Sea Island 
and Egyptian varieties, as well as in some of the Upland sorts, the 
bracts are not merely divided to the base, but they often have the 
low^er corners rolled back, thus leaving an open passage for the 
weevils. The Rabinal cotton much excels all the other varieties thus 



38 WEEVIL-RESISTTNG ADAPTATIONS OF COTTON. 

far studied in the extent to which the bracts are grown together at 
the base. Sometimes they are united for a quarter or even a third 
of their length. (PL IV," fig. 1, and -PL X, fig. 1.) 

APPRESSED ]MARGINS OF BRACTS. 

In both of these Gucltemahm varieties the margins of the bracts of 
young invobicres are firmly and closely appressed, in strilving con- 
trast with the Sea Ishind and Pjgyptian varieties, where the Vxid is 
commonly exposed e\'eii when very young. This form of i^rotection 
is effective while it lasts, but in the Rabinal cotton the involucre is 
too small, and the growth of the young bud soon separates the bracts 
and permits the entraiu-e of the weevil. The United States Upland 
varieties are intermediate between the Sea Island and the Kekchi cot- 
tons in the degree to which the involncres are closed and the margins 
fitted together. A large proportion of the Upland involucres give 
ready access to the weevils, while most of those of the Kekchi cotton 
remain effectively closed for a longer jjeriod, as will be understood 
after a survey of the other involucral characters which conduce to 
the same resnlt. 

In one respect the firmly closed involucres of the Rabinal cotton 
seemed almost like an advantage to the Aveevil rather than the con- 
trary, for the insect is not admitted to the bud until it is about large 
enough to furnish a place of development for a larva. The plant 
having taken control, as it w^ere, of this relation, the weevils have not 
needed to possess an instinct against the destruction of 5^oung buds. 
Those of the open involucred Sea Island varieties often were attacked 
while still altogether too small to bring a larva to maturity. The 
advantage of the closed involucres lies, no doubt, in the fact that they 
shorten the period of access and allow some of the buds to escape 
which would be punctured either for feeding or for egg laying if the 
weevil has a longer opportunity. (PI. IV.) 

The Rabinal cotton culture is that in which the plants are cut 
back yearly to the ground. During the next month, or until the buds 
begin to develop on the new^ shoots, the weevils have no breeding 
places and nothing to feed upon except the leaves and leaf buds. In 
patches where the weevils are abundant the leaf buds are eaten out 
so persistently as to seriously interfere with the growth of the plants, 
and the very young floAver buds were also reached in some instances 
by boring through the involucres. When attacked at this stage the 
buds wdther and drop off. They serve the w-eevils only for feeding 
purposes, and their use in this way only postpones the time "when 
breeding can be resumed. 

The cotton at Rabinal was often overrun by two species of small 
black ants, identified by Dr. W. H. Ashmead as belonging to the 



LARGE INVOLUCRES OF KEKCHI COTTON. 39 

genera Solenopsis and Tapinoma.'* There was no indication, how- 
ever, that these afforded any protection against the weevils, although 
they might, perhaps, act as Avatchmen and scare weevils away when 
they happened to be present on buds or bolls where weevils had 
alighted, like other small ants which have been reported as attacking 
the boll weevil. The keleps belong in an entirely distinct category 
in being able to sting and carry off the weevils and make regular use 
of them as food. Instead of being of service to the cotton these 
small ants at Rabinal were a distinct injury; the Solenopsis was 
taking care of plant lice,'' which often infested the cotton to a 
decidedly harmful extent. It continues and supplements the work 
of the boll weevils in stunting and distorting the plants. When the 
aphids are very numerous, the leaves are badly curled and growth is 
greatly impeded. 

LARGE INVOLUCRES OF KEKCHI COTTON. 

The Kekchi cotton has the bracts of the involucre much larger in 
proportion to the contained bud than the Rabinal cotton or than any 
of our Upland varieties. The possession of larger bracts constitutes 
a distinct weevil-resisting adaptation, since it permits the involucre 
to be more effectively closed and the protection to be continued for a 
longer time. Sooner or later, of course, the bracts must be separated 
by the growing bud. The larger the bracts the longer the bud can 
continue to grow before spreading the bracts apart. (PI. IX, fig. 1.) 

Prof. II. Pittier, who had charge of the Secanquim experiment in 
the latter part of the season, was especially impressed with the pro- 
tective utility of the larger bracts of the Kekchi cotton, as shown by 
the following summary of his observations: 

The large size of the bracts in proportion to the floral bud is a very important 
protective feature. In the Kekchi cotton the amplitude of these bracts is such 
as to completely inclose the bud at all times before the anthesis. and even in 
cases when they happen to be slightly separated the occlusion is maintained by 
the long hairs which fringe them on all sides. The length of these hairs con- 
stitutes a serious obstacle to the progress of the weevils, whose tarsi can not 
obtain a firm hold on the solid surface. I have seen them droit to the ground 
after many awkward attempts to gain access to the squares, while on the other 
hand the keleps did not seem to be impeded at all by the bristles. 

" The material was not sufficient for a conclusive determination of the species. 
I)(((tor Ashmead says: "You have two distinct species of ants here. One, No. 
1, belongs to the family ]\Iyrmicid;Tp and is apparently the worker of (Solenopsis 
pieea Emery ; the other. No. 2, belongs to the family Dolichoderidiv and is 
apparently the worker of Tvpinonia raiinilonini Emery. I am sorry you did 
not have the different sexes, so that I could make positive of the species. In 
Solenopsis, as you probably know, there are four or live different forms, and it 
is not easy to identify from a single form.'" 

6 These have been identified by :\Ir. Theodore Pergande as Aphis f/ossi/pii, a 
species well known in the United States. 



40 



WEEVIL-RESTSTING ADAPTATIONS OF COTTON. 



To show the increased size of the bracts in the Kekchi cotton, I have carefully 
measui'ed over 250 squares of five of the most promising varieties of the Upland 
species. The dimensions taken were the length of the floral bud, and the length 
and bi'eadth of the bracts. The table, in which these data are condensed in a 
comprehensive form, shows a decided advantage in favor of the Kekchi cotton. 

Table I. — Dimensions of pnrol hiids and bracts of sercral rarirtirs of coiion 

compared. 



Length of 

floral bud 

(millimeters). 


Kekchi. 


Parker. 


King. 


Allen. 


Jewett. 

1 


O 


o 

.a o 

mm. 
20 
28 
39 
42 
42 
42 
47 
52 
37 
47 
42 




^t 

w 

w 

mm. 
11 
18 
27 
30 
30 
30 
33 
30 
27 
36 
30 


C(-t 


CM 



mm. 


O 

IS 
m 

mm. 


CM 
O 


o 

►J 
m.m. 


1-1 

o 

St 


o 

0) to 




o 


o 
+^ o 


CM 

o 


CM 
O 


CM ! 



■Si 

SI ,Q 


5- 6 


1 
1 

6 
5 
3 
4 
3 

! 

3 
2 


mm. 


m.m,. 


mm. 




mm. 


wtm. 


7- 8 


2 
13 
16 

18 
8 
6 
3 
3 
1 
3 
2 
2 
1 


25 
31 
36 
39 
38 
39 
43 
48 
36 
■SJ 
44 
45 
47 


19 
20 
24 
25 
23 
26 
24 
26 
25 
25 
25 
24 
30 








1 

18 
10 
18 
13 
5 
1 
1 
5 
1 
5 


26 
34 
34 
37 
39 
39 
49 
40 
40 
33 
42 


20 
21 
23 
23 
24 
25 
29 
26 
23 
21 
25 








9-10 


5 

. 7 

I 

6 

4 
1 
2 


33 
34 

40 
44 
40 
43 
43 
41 


19 
23 
24 
25 
24 
26 
25 
26 


3 
2 

10 

5 

1 


38 
36 
39 
41 
39 
52 
47 


26 
21 
26 
28 
i» 
38 
34 


11-12 


13-14_. 


15-16 


17-18_ 

19-20 


21-22 


23-24 

25-26 


1 


48 


33 


27-28_ 


2 
1 


40 
49 


25 

28 


29-80 _-.. 


, 












31-32 




















33-34 




















1 
32 


42 


32 


Total.. 


31 






78 






48 






li" 
























1 



The advantage i.s particularly notable with respect to the greater 
width of the bracts, which enables them to remain much more effect- 
ively closed at the angles. In the Parker. King, and Allen varieties 
the bracts very seldom attain a width of 30 mm., while in the Kekchi 
cotton the average width for all except the smallest buds is above 
30 mm. 

OPENING, OR FLARING, OF BRACTS AVOIDED. 

The unusually large and well-closed bracts of the Kekchi cotton 
have another practical use in keeping the bud from drying out, as 
explained in the discussion of proliferation. 

The external indication of this difference is that in the Kekchi 
cotton punctured squares commonly do not open, or flare, by the 
spreading apart of the involucral bracts, while among the Upland 
and Sea Island varieties flaring is the regular rule. Quite a per- 
centage of the squares of Abbasi, Parker. King, and other varieties 
stand well open normally before any injury has occurred, but the 
Kekchi cotton seldom or never exposes its squares before flowering. 
The larger and broader involucre is also able to permit the protrusion 
of the flower without losing the power of closing and remaining 
shut for a considerable period after flowering, while the Parker and 
King varieties often remain quite open, so that the young boll is 
fully exposed to the weevils. 



■ EXTENT OF PROTECTION BY INVOLUCRE. 41 

All exaiiipk' of the pr()nn)tness with which weevil injuries cause 
the involucres of our Upland cotton to open is well shown in a note 
by Mr. McLachlan : 

On August 8, at 2 p. in., a small cage was placed over a small i)lant of Parker 
cotton, and .1 female and 2 male weevils were introdueeil. The plant jwssessed 
?.G squares. 4 flowers, and 9 bolls. The morning after the weevils were put 
into the cage several of the scpiares had flared and one had fallen. It would 
seem that the mechanical forces of the square are quickly affected by the woi-k 
of the weevils. Here, of course, the punctures were numerous, because of the 
many weevils on the plant. Some of the squares were riddled with feeding 
and egg punctures. 

The buds of Kekchi cotton often recover from three or four punc- 
tures, though they might not do so if these were all made at the same 
time. But it often happens that squares with numerous feeding 
punctures remain closed and wither up Avithout flaring. 

HAIRY 3IARCJ1NS OF INVOLUCRAL BRACTS. 

In addition to their larger size, the bracts of the Kekclii cotton have 
the marginal teeth or lacinia^ more numerous and more hairy than 
those of our Upland varieties and able to afford more of an impedi- 
ment to the entrance of the weevils. The difference was very pro- 
nounced in our experimental plot, where King, Parker, and other 
familiar American sorts were planted beside the Kekchi. It is as 
superior in this respect to the other Upland varieties as they are to 
the Sea Island. 

The Kekchi and Kabinal varieties, though both belonging to the 
Upland series and having many similarities, have also very distinct 
differences, as, for example, in the present character. The small, 
firmly appressed bracts of the Rabinal cotton have the marginal 
lacinia' few and small ; sometimes the edges are nearly entire, or 
merely toothed. The liaiiy covering is also reduced to a fine, short 
coat, which can afford little or no impediment to the weevils. 

EXTENT OF PROTECTION BY INVOLUCRE. 

That the closed involucres do indeed contribute to the protection of 
the young buds from the weevils became very obvious in one of our 
experimental plots at Secanquim, located about a quarter of a mile 
outside the belt of Indian cultivation of cotton. There being no 
keleps to afford protection, the cotton soon became thickly infested 
with weevils, and very few bolls were allowed to develop on any of 
the plants. There was a notable difference, however, in the age at 
which the buds were punctured. As already stated, the edges of the 
bracts of some of the Sea Island and Egyptian varieties separate at 
a much earlier period than those of the Upland varieties, and the 



•i2 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

weevils commonly attack them in their very early stages, and even 
Avhile they are altogether too small to jiermit the development of a 
weevil larva. It has been pointed out already by Messrs. Hunter 
and Hinds that the smooth stems and petioles of the Sea Island and 
Egyptian cottons render them nnich more readily susceptible to 
injury by the boll w'eevil than are the Upland types, and if we add 
to this the disadvantage arising from the later development and the 
more open involucres the possibility of protecting the long-staple 
cottons against the Aveevils seems small indeed. 

Instead of being immune to the boll weevil, as at one time hoped, 
the Egyptian and Sea Island -varieties seem to be most lacking in 
weevil-resisting adaptations, as might, indeed, have been expected in 
view of the fact that they have been developed in regions to which the 
weevil has not yet penetrated. The Kidney cottons, which may be 
looked upon as representing the Sea Island type on the mainland of 
the American continents, have, as will be seen later, a peculiar 
feature of protective value. 

ADVANTAGE OF OPEN INVOLUCRES. 

It will be apparent from the facts already recited that the partly 
closed involucres of the Sea Island and Upland varieties now culti- 
vated in the United States serve little or no purpose in resisting the 
boll weevil. On the contrary, they often appeal' to be an advantage 
to the insect, serving, as they do, to hide the parasite from its enemies 
and protect it against the application of insecticides or capture by 
insectivorous birds." 

The great variation in the size and shape of the involucre in the 
different varieties of cotton suggests the practicability of securing 
sorts with open involucres or with these structures reduced to small 
dimensions. If the weevils Avere to be caught by insecti^'orous l)irds, 
like the Cuban oriole, Avhose Aveevil-eating habits have lieen discovered 
by Mr. E. A. Schwarz, open involucres Avoukl be a distinct advantage. 
It might then be possible also to apply Paris green or other insecti- 
cides to young buds which are, except in the early spring, the 
exclusive feeding places of the weevils. 

The practicability of an open involucre Avill need, however, to be 
considered from another standpoint. It must be ascertained whether 
the young buds will bear full exposure. Unlike most of the related 
plants, the cotton bud is not protected by a calj^x. The inA'olucre may 
be necessary as a substitute, especially in dry climates. In humid 

a Dr. H. J. Webber states that the desirability of open invohicres has been 
appreciated and that selections of Upland varieties with a view to the develop- 
ment of this character have be^u made. 



BEHAVTOR OF PARASITIZED BUDS. 43 

regions, hoAvevor, this iv(iuireiuent might be rehixed, and it is in such 
places that the injuries of the Aveevils are the greatest/' 

BEHAVIOR OF PARASITIZED BUDS. 

SHEDDING OF WEEVIL-IXFESTED SQUARES. 

In a dry climate, like that of the Mexican plateau region, the drop- 
ping of the squares in which the weevils have deposited eggs would 
constitute a very effective adaptation. The weevil larA'je do not sur- 
vive a thorough drying out of the squares. It is only in the arid 
districts of Mexico that the cotton plant has shown its ability to 
escape from cultivation and maintain itself Avithout human assistance, 
if indeed it be not in some places a truly indigenous wild plant, as 
several botanists have reported. But in a moist region like the cotton 
belt of eastern Texas this habit of the plant has no practical use, 
since as many of the weevils die when the injured squares remain 
attached to the plant as Avhen they fall to the ground. 

" It is generally true that scjuares seriously injured by the weevil sooner or 
later fall to the jjround. Some plants, however, shed the injured s(iuares more 
readily. than do others. It seems to be a matter of individual variation rather 
than a varietal character. Thus occasional plants retain a large proportion of 
their infested squares, which hang by the very tip of the base of the stem. 
Normally the squares are shed because of the formation of an absciss layer 
of corky tissue across their junction with the stem. In the case of the squares 
which remain hanging, the foi'mation of this layer seems to be incomplete, or 
else it becomes formed in an unusual plane, so that while the square is effectu- 
ally cut off, it merely falls over and hangs by a bit of bark at its tii). In this 
|)osition it dries thoroughly and becomes of a dark brown color. Plants 
showing () or 8 of these dried brown squares are quite conmion in infested 
fields. Although exposeil to complete drying and the direct rays of the sun, 
the larva:" within are not all destroyed. * * * 

" It seems a conservative estimate, therefore, to say that fully one-third of 
these exposed dried squares may be expected to produce adults. Considering 
the exposed condition of such squares this seems to be a very high percent- 
rjge * * * rpjjg observations made, however, certainly show that a complete 

o After the above had been written it was observed that the Pachon cotton 
from western Guatemala, grown in an experimental plot at Lanham, iMd., has 
the peculiar feature of a large calyx, which completely covers the young bud 
and extends above it into long, slender, hairy tips. It may be that this is to be 
looked upon as still another weevil-resisting adaptation. The weevils would be 
able, undoubtedly, to bore through the calyx, but the hairy tips might hinder 
their access to the bud. The l)racts are much smaller and much more oi)en 
than in the Kekchi and Rabinal varieties, but the laciniie, or teeth, along their 
margins are rather stiff and are clothed with nmnerous hairs, sti'onger and 
more bristlelike than in the Kekchi and Rabinal varieties, and able to keep the 
lacinife from closing together. It may be that the greater rigidity of the lacinia> 
and the bristles gives better protection than the open position of the bracts 
would indicate. The case is in reality quite different from that of the Sea 
Island varieties, where the bracts are both naked and open. 



44 WEEVIL-RESISTIKG ADAPTATIONS OF COTTON. 

(Iryiiifi (if the s(iii;ire does not necessarily destroy the lai'\:i, and that a square 
may undei'go far more exposure to direct sunshine than had been su])posed 
l)Ossil)Ie 'without causing the death of the hirva or pupa within." a 

It is to be remembered, however, that such disconnected squares are 
thoroughly dampened every night by the dew. and that a small 
amount of moisture may pass out from the plant through the shred 
of dead tissue. In either case the hanging boll might get more moist- 
ure and less heat than if lying on the dry ground, exposed to fnll 
sunlight. Suspended bolls are exposed to air temperatures only. 

If no other means of avoiding the weevil becomes practicable a 
great extension of the cotton production into the semiarid districts of 
western Texas, Oklahoma, and even Kansas is to be expected. The 
long days of the more northern districts will conduce to the shorten- 
ing of the growing season, and if dry weather cuts down the yield the 
loss is likely to be neutralized by more or less complete protection 
against the weevils. 

These contradictory effects of the same adaptation depending upon 
climatic condition may render necessary a complete differentiation of 
the cotton varieties of wet and dry regions. 

It is not improbable that the Upland varieties previously known in 
the United States came originally from the more or less arid regions 
of Mexico, where absence or very small developme'nt of the basal 
branches keeps the ground from being constantly shaded and gives 
better chances for the weevils to be killed by the drying out of the 
fallen squares. 

Our Upland cottons are undoubtedly of American origin, but the 
region from Avhich they came has not been ascertained. Some of the 
Texas varieties are said to have l)een brought from Mexico. Coro- 
nado's Journal of the earliest Spanish exploration in Arizona and 
New Mexico contains many references to the cultivation of cotton by 
the Indians. There can be little doubt that the agricultural Indians 
of the Gulf region also cultivated cotton, though no documentary 
evidence of the fact seems to have come to light as yet. 

It is highly probable that the original home of the cotton plant, and 
of the boll weevil as well, was in a somewhat arid region, since it is 
onl}" under such conditions that the weevil would be effectually pre- 
vented from increasing to the fatal degree of destroying its host 
])lant, and thus cutting off' its only means of subsistence. On the 
other hand, it was only in a humid countr}^ like eastern Guatemala 
that many of these weevil-resisting adaptations would be likely to 
develop if, as now appears, it has required the selective influence of 
the boll weevil itself to bring them to their present advanced develop- 
ment. 

a Hnnter, W. D., and Hinds, W. E.. 11M)4. The Mexican Cotton Boll Weevil. 
Bui. 45, Division of Entomology, U. S. Department of Agriculture, pp. 73 and 74. 



COUNTINGS OF FLARED AND FALLEN SQUARES. 45 

The adaptive character of this habit of shedding the parasitized 
squares seems to be conhnned by the fact that it depends upon the 
existence of a sjjecial layer of soft cells Avhich readily break down 
when the bud is injured. Many plants have such cells as a means of 
shedding their fruits, !)ut they seem not to be prevalent among the 
relatives of the cotton. The cotton itself does not drop the ripe bolls, 
and even the empty shell often remains long after the seeds are gone. 

The drier the climate the more effective is the prompt shedding of 
injured squares. AVhether there are other adaptations thus especially 
suited to dry climates is not yet knoAvn, our studies having l)een con- 
fined mostly to humid regions. 

Dr. Edward Palmer, who has spent many years in botanical ex- 
plorations of the dry plateau region of Mexico and who discovered 
that the boll Aveevil was a cotton pest, states that in several localities 
where the cotton was formerly grown without difficulty the introduc- 
tion of irrigation improvements has proved disastrous. With the 
assistance of the moist soil the weevils are now able to reach maturity 
in large numl)ers and complete the devastation of the crop, (piite as 
in Texas. The irrigated soil affords a situation favorable for the 
development of the larva> in the fallen squares. 

This is said to have been the case about Parras, and at Rio Verde, 
below San Luis Potosi. The culture of cotton has declined also in 
the "Huasteca Potosina,'' the tropical district l)etween San Luis and 
Tampico, and on the Pacific side of Mexico, along the Santiago River 
above San Bias, as well as about Tepic. Doctor Palmer saAv cotton 
growing in a wild condition in the fences at the old nussion, San Jose 
de Guaynuis, (> miles from the commercial port; again at Mulege, 
LoAver California, across the Gulf from Guaymas, the latter a much- 
branched, prolific tree, producing a nankeen-colored lint. About 
Guaymas cotton was formerly utilized by the Indians as tinder, after 
being dipped in a solution of saltpeter. The same facts were observed 
by Dr. L. O. Howard in ISOf) at San Jose de Guaymas. 

COUNTINGS OF FLARED AND FALLEN SQLTARES. 

An attempt was made in connection with our Guatemalan experi- 
ment to secure data on which a definite statement might be based 
regarding the extent to which the different varieties were protected 
by their involucral characters, but the problems are too complex to 
be reached except by more elaborate statistical studies than were prac- 
ticable at that time. 

Countings were made, for example, of the flared and fallen 
squares — that is, of those which it might be supposed that the weevils 
have injured — and of the number of weevil larvte, proliferations, etc., 
found inside them. The results in percentages do not agree, however. 



46 WEEVIL-KESrSTlNd ADAPTATIONS OF COTTON. 

with the facts obvious m the fields: indeed, they greatly misrepre- 
sent them. Thus the j^ercenlage of Aveevil injuries in flared and 
fallen squares does not appear very much higher in the Kekchi cotton 
than in the Sea Island and Upland varieties; yet as a matter of 
fact the squares of the Kekchi cotton seldom flared for any other 
reason than Aveevil injuries, and much less often for this cause than 
did those of other varieties. Many small squares of the Kekchi cot- 
ton fall off, however, before they are large enough or open enough 
to be attacked by the weevils." This takes place in the other varie- 
ties to a much smaller extent, but with them the apparent percentage 
of Aveevil injuries among flared squares is much diminished, because 
many squares stand open and appear as though beginning to flare, 
even before the weevils have attacked them. 

PROLIFERATION OF INTERNAL TISSUES OF BUDS. 

The protection of the buds does not end with devices for the exclu- 
sion of the adult weevils, nor with the rejection of those in which they 
have laid their eggs. It is also possible for the plant to heal the 
wound, and bring the injured bud to maturity by preventing the 
growth of the weevil larva. Where the climate is dry the Aveevil 
iarva^ in the rejected Inids are killed, as already explained. The 
humid climate alternative of the falling of the parasitized squares is 
proliferation, the growth inside the l)ud of loose, watery tissue in 
which the larva does not develop. Whether the larva is killed by 
smothering, starving, or poisoning, or by some combination of these, 
is not yet known. Starvation is a sufficient explanation, since the 
material with which the larva becomes surrounded can ):ie no adequate 
substitute for the highly nutritious pollen grains on which the infant 
larva Avould otherwise feed. 

Proliferation is much more frequent in the Kekchi cotton than in 
any of our United States varieties, as far as known. The first and 
second punctures are commonly resisted successfully, but the third, 
fourth, or fifth attempt may succeed in the development of a larva. 
The proportion oi weevil jjunctures rendered ineffective by prolifera- 
tion was found to run well above ."iO per cent, sometimes between 80 
and 1)0. (PI. V.) 

The promptness and efficiency of proliferation bear an inverse pro- 
portion to the size of the buds. As the latter grow larger the mass of 
anthers inside becomes less compact, and the other tissues become too 

a Professor Pittier found in the latter pai't of the season that the buds of 
the Kekchi cotton were sometimes cut away at the base and left hanging in a 
wilted condition. These were at first taken for flared squares as the result 
of weevil injuries. Init it was later ascertained that this was not the case, 
though the true cause was not learned. The damage was done in the night. 



PROLIFERATION OF INTERNAL TISSUES OF BUDS. 47 

nearly mature to put forth new <j;ro\vth. If the preseiiee of the hirva 
at this stage is sufficient to cause the bud to fall otf, the development 
of the parasite to maturity is well assured, the large bud aifording 
good protection and adequate food. . . 

In the Kekchi cotton, howeA'er, such late attacks very seldom cause 
the bud to fall off. Larva) developed in the larger buds are turned 
out of doors, as it were, by the opening of the flower. The tendency 
of injured buds to persist is notably greater than in the United 
States, either because of some physiological difference between the 
varieties, or because of the larger and more firmly closed involucres 
qf the Kekchi cotton, which keep the buds surrounded with a moist 
atmosphere and protect it against drying out Avhile the new tissues 
are forming to heal the wound and encvst the ego;. 

In the closely planted Indian fields the squares seldom flare as in 
the Texas varieties. They generally remain in place and continue to 
grow until the bracts have reached nearh' their full normal size. In 
fields partiall}' protected by the keleps the Aveevil larvcT do not 
seem to develop in buds as small as in Texas. Proliferation may 
partW explain this delay and also the more firmly closed involucres, 
but in our unprotected plot the weevils were able by repeated punc- 
tures to infest smaller squares and reach maturity in them, after they 
had fallen to the ground. 

The behavior of w^eevil larvse inside the squares in (jruatemala 
seems also to differ appreciably from that observed in Texas where 
younger squares are usuall}- much more accessible to the weevils, and 
are commonly punctured. In Texas the larvjie regularly grow to 
maturity, depending for food upon the pollen, which is completely 
eaten out. In Guatemala this ver}^ seldom occurs. Small squares 
with well-developed weevil larva^ are rarely found imder normal con- 
ditions, nor do the larvsc depend upon the pollen as their principal 
article of diet, as in Texas. 

Several reasons for this difference may be considered. The first is 
that the larger and more firmly closed involucre of the Kekchi cotton 
gives the buds several days of protection, so that the average size 
would naturally l)e larger. The examination of large numbers of 
squares picked at random from the Indian cotton fields by Messrs. 
Kinsler and McLachlan shoAv also that a very large proportion of the 
punctures are followed by proliferation, and that this means of pro- 
tection is much more efficient in the younger squares. Another rea- 
son must be sought, hoAvever, for the failure of the larvse to eat the 
pollen of the large buds where proliferation is less prompt and less 
frequent. The impression might be gained that the pollen of the 
Kekchi cotton is in some Avay not accei^table to the weevils, since even 
w^hen there is an abundance of pollen at hand they prefer to eat out 



48 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

the .style and central column of the Hower, and thence down into the 
ovary or young boll. After this has been consumed the larvae return 
to the upper part of the bud to finish the remainder of the pollen. 

Nevertheless, this suggestion of a protecting quality in the pollen 
itself can not be accepted with much confidence because the weevils 
showed in numerous instances that they could live and thrive upon the 
pollen of the young squares, quite as in the United States. This oc- 
curred in the experimental plot where there were no keleps, and the 
weevils were very numerous and persistent in their attacks. After 
two or three jDunctures the squares flared and fell to the ground in 
the usual manner, and in these the weevil larvae were able to reach 
maturity. 

A more probable reason for the usua.1 failure of the larva? to eat the 
pollen as freely as in the United States is furnished by the opinion of 
Mr. W. I). Hunter, that the original habit of the weevil way to attack 
t]ie bolls, like related species of Anthonomus, which live upon various 
kinds of fruits." If this be true with reference to the boll weevil we 
may think of the Guatemalan members of the species as having 
retained somewhat more of the ancestral habits which with them are 
definitely useful, because the cotton variety with which they have to 
deal has j^erfected, to x larger extent than the Texas varieties, the art 
of proliferation. 

As a further indication of the greater strength among the Guate- 
malan weevils of the instinct of attacking the ovary of the bud 
may be mentioned the fact that a very large proportion of the 
punctures occur Ioav down — that is. on or below the level of the apex 
of the young boll. The larva commonly eats directlv to the center of 
the bud and hollows out the apex of the young boll. This habit 
gives rather less opportunity for successful proliferation than in 
Texas, because the cavity hollowed out b}^ the larA^a lies below the 
level of the staminal tube, the tissues of which are the most active 
m proliferation. The Kekchi cotton shows occasionally anothei- 
form of proliferation not recorded from Texas, namely, that of the 
base of the corolla. Sometimes this enlargement takes place in an 
outward direction, forming a wart or protuberance on one side 
of the bud, as shown in Plate VI. In other instances the direc- 
tion is reversed and the ingrowing edges of the wound made by 
th* weevil fill the internal cavity and prevent the development 
of the larva. The proliferation of the corolla, besides being less 

"A new species of Antliouoiuus with liabits closely identical with those of the 
boll weevil, l>ut parasitic on the pepper plant (Capsicum), has been discovered 
recently in Texas by Mr. E. A. Schwarz. This gains an added interest from the 
fact already noted that it is the regular custom of the Indians of Alta Vera 
Paz to plant peppers among the cotton. 



CAUSES AND CONDITIONS OF BUD PROLIFERATION. 49 

frequent than that of the staniinal tube, is probably also less elect- 
ive, since the weevil larva^ could escape before it into the ct",ter of 
the flower while the proliferation from the staniinal tube groAvs 
outward, as though to meet the intruder and keep him separated 
from the more special organs. 

The habit of the larvie to seek the center of the bud and gnaw^ 
off the style is responsible for the loss of large numbers of younger 
bolls Avhich have suffered no direct injury from the weevil. Even 
though the larva be subsequently killed by proliferation or though 
the flower dro])s off and carries the larva with it, the lack of polli- 
nation must prevent the development of the young boll unless par- 
y thenogenesis takes place, which seems improbable. 

Larva^ were found in several instances in nearly full-sized buds 
about to open, and in another case a more than half-grown larva 
was found inside the central column of an open flower. More or less 
distorted flowers with unmistakable signs of previous proliferation 
in the bud stages are commonly found in the Kekchi cotton fields. 

Summarizing the results of the study of proliferation in the 
Kekchi' cotton, it may be said that although the frequency of pro- 
liferation in the young squares is very great, its efficiency in prevent- 
ing the breeding of the weevils is someAvhat less than might be ex- 
pected in Texas, owing to the difference of food habits among the 
weevils. If the Texas weevils are as consistent in their habits as 
now supposed, the introduction of the Kekchi cotton or of a similar 
proliferating variety might be of great benefit as a preventive 
measure. The extent, however, to which it could be made to compass 
the complete destruction of the weevil would depend someAvhat upon 
the degree, if any, to Avhich they might return to the habit shoAvn in 
Guatemala of feeding upon the ovaries or boll rudiments rather 
than upon the pollen of the young buds, an important and hitherto 
unsuspected difference in habits betAveen the Aveevils of Texas and 
those of Guatemala. 

CAUSES AND CONDITIONS OF Bl I) I'UOLIFEHATION. 

That the i)roliferation is occasioned by the injuries of the weevil is 
too obvious to admit of doubt, but it may be of much practical 
importance to learn the exact Avay in which the ucav growth of tissue 
is brought about. The disturbing factor might be either mechanical 
or chemical. The new growth nuiy be a direct response to injury of 
the AveeA'ils in feeding or laying eggs, or it might be stinudated indi- 
rectly by the secretions of the yoimg larva, or by chemical changes 
or decay of the damaged tissue. A second mechanical possibility is 
that of pressure developed in the young and rapidly groAving bud. 
99G2— No. 88—05 m 4 



50 \VEEVlL-RESISTIN('r ADAPTATIONS OF COTTON. 

The bun'owiiiii' of tlic weevil ivlieves this pressure at one point, and 
may thus furnish the exciting cause of the rapid growth in this direc- 
tion of the tissue of the staniinal tube. 

It seems not improbable that a relation will l)e found between the 
method of culture and the extent and frequency of proliferation. 
Open-field conditions, with much bare ground about the plants, would 
increase the daily exposure of heat and dry air, and this would con- 
duce to the wilting of the punctured squares, which might then be 
expected to flare and fall off instead of remaining to proliferate. The 
result of weevil work in our open-culture plots was obviously differ- 
ent from that in the more crowded cotton fields of the Indians. On 
the widely separated plants the squares often fell off and permitted 
the larvae to develop, as in Texas, except that there was still a distinct 
tendency on the part of the larvte to attack the pistil and ovary first, 
before eating out the pollen. 

PROLIFERATION IN OTHER VARIETIES. 

l^roliferation is by no means confined to the Kekchi cotton, but 
probably occurs, occasionally at least, in all the Upland and Sea 
Island varieties. A noteworthy Guatemalan Sea Island cotton w-as 
found by Mr. Kinsler in the aldea of San Lucas, a few miles from 
Secanquim." Both the buds and the bolls afforded fine examples of 
effective proliferation. Even the P^gyptian varieties showed a dis- 
tinct ability in this direction. In one instance no less than 17 of 23 
punctured squares of Jannovitch had proliferated, and 15 cases 
seemed to have been effective. 

Proliferation ceases to occur when the bud has become too large. 
The anthers are no longer so closely packed together and the tissues 
of the staniinal tube are too nearly mature. By that time, how^ever, 
the style may be sufficiently developed to furnish adequate food. 
It is well known, hoAvever, that the period of development of the 
weevil larvte may be greatly prolonged, and this would seem likely 
in the present instance, since the tissues of the styles must be less 
nutritious than the pollen. The delay also would be advantageous, 
since it w'ould permit the young boll to become larger. 

a This variety is iieculiar in having about half of each seed covei-ed only with a 
very tine, short, bright I)lnish-green lint. The upper half bears the long white 
fiber, and is smooth and I)ladv when this has been removed. Some of the 
plants had excellent crops of bolls, unusually uniform in size and apparent age, 
as though the habit of seasonal flowering were well accentuated. The variety 
is evidently perennial and grows to a height of from 6 to 8 feet, but on the 
(Other plants the leaves, flowers, and bolls were much reduced in size. The; 
plants w«*r(& ;ill occupied by small black ants. On some of them no weevils nor 
any indications of weevil injury were found, but others only a few rods away 
^ere badly infested. 



PROTECTTON OF THE BOLLS. 51 

But as the power of eifective proliferation declines in the larger 
buds another factor of protection comes into play. The later the 
attack of the weevil the greater is the chance that the l)ud will mature 
and the flower Avill open and turn the weevil larva out of its qiuirters 
to die. And since l)uds commonly mature which have been attacked 
while still young enough to proliferate, it is easy to understand why 
attacks made in the later stages seem to be eifective only in excep- 
tional instances. 

An element of uncertainty often attaches to the enumeration of 
weevil injuries because of the difficulty of finding the egg or very 
young larvse of the weevil in the squares which have been only 
recently attacked. This is especially true in small squares where the 
anthers are still white and of about the same color, size, and general 
appearance as the eggs. The jjossible error does not, however, mate- 
rially affect the result, since it is to be expected that the same propor- 
tion of bolls will proliferate and the same percentage of weevil 
larva' develop as in the squares which are far enough advanced to 
show definite residts. 

PROTECTION OF THE BOLLS. 

If it be true, as already intimated, that the original habit of the 
weevil was to attack the boll instead of the bud, the opportunity for 
the selective development of protective characters of the boll has 
been greater. This suggestion seems to accord with the results, 
since the boll of the Kekchi cotton has a series of protective characters 
even more striking and effective than those of the involucre and the 
bud. 

PERSISTENCE OF FLOWERS. 

As long as the flower remains in place the young boll is thoroughly 
protected, the weevils having no means of access except by boring 
thi'ough the withering tissues, Avhich seems not to be attempted. In 
the Kekchi cotton the flow er falls only when detached by the swelling 
of the young boll. This may also be true of other varieties. (See 
PL IX.) 

The frequent sequel of proliferation in the bud, as noted above, is 
the loss of the young boll through lack of i^ollination. This is espe- 
cially true in Guatemala, owing to the tendency of the w^eevil larva* 
to eat away the style. On one occasion Mr. Kinsler collected from a 
field of Indian cotton 28 young bolls showing signs of debility. These 
measured from 18 to '20 mm. in length, most of them about 15 mm. 
None of the smaller bolls showed signs of weevil injury, but in many 
of them the ovules were already sliriveling up. A few punctures were 
found in some of the larger bolls, and in some of these proliferation 
had occurred. The development of the weevil larva* to maturity 



52 WEEVTL-RESISTING ADAPTATIONS OF COTTON. 

i^eeiiied unlikely in any case, because the unfertilized ovules were 
already withering. 

Presumably there are various stages and degrees of fertilization. 
Some of the stigmas of proliferated buds seem to have adecjuate 
polleu, so that the bolls can develop normally, while others obtain 
none at all or only a little. The persistence of injured flowers is 
much greater. They may not fall off at all, and often remain at- 
tached by the withered style to the boll when nearly full size. 

It thus happens that injured flowers protect their young bolls 
longer than the others, but in most instances such bolls renuiin small 
or unsymmetrical, presumably as a result of inadequate fertilization. 
It is quite possible, however, for normal bolls to develop occasionally 
from weevil-infested buds Avhich never open, for the style often 
pushes through and becomes fully exposed, so that fertilization by 
pollen from another flower might readily take place. 

IMMUNITY OF VERY YOUNG BOLLS. 

For reasons not yet ascertained, the weevils in Guatemala seldom 
or never attacked the A^ery young bolls. This may be due to a con- 
servative instinct on the part of the weevil, like that wdiich forbids 
the laying of any additional eggs in a bud already parasitized." It 
is not impossible, however, that the oil glands with which the sur- 
face of the young boll is very thickly beset nuiy have a protective 
function. As the boll growls larger the glands do not appear to 
increase in numbers, but become separated much more widely. On 
bolls of the Kekchi cotton the oil glands are usually al)sent from a 
distinct longitudinal band running down the middle of each carpel. 
(PL VII.) A large proportion of the weevil egg punctures are 
made along this naked band, although very few of them take effect. 
The w^all is thicker here, and the w^eevil in boring meets the tough 
lining of the boll chamber at an angle, and is seldom able to penetrate. 
If this interpretation of the facts be correct, the naked band consti- 
tutes a veritable Aveevil trap, a device for inducing the weevil to 
make its punctures and lay its eggs in the part of the boll where they 
can do no harm.'' 

To ascribe a protective value to the oil glands is not unreason- 
able in view of the fact reported by Messrs. Quaintance and Brues, 

o Hunter. W. D.. and Hinds. W. E., 1005. The Mexican Cotton Roll Weevil. 
Bui. 51. Bureau of Entomology. V. !^. Department of Agriculture, p. 7S. 

6 This peculiarity of a glandless longitudinal band in the middle of each 
carpel was also noticed in a variety of cotton cultivated I)y the Moqui Indians 
of Arizona, grown in 1904. in the Department's ]ilant-l)reeding experimental 
field at Terrell. Tex. The Moqui cotton is interesting also by reason of its 
short, squarish, distinctly apiculate bolls, more like some of the Old World 
cottons than are those of other members of the Upland series. 



IMMUNITY OF VERY YOUNG BOLLS. 53 

that the Egyptian cotton, the bolls of which arc excessively oily, is 
on this acconnt innnnne from the holhvonn." The oil contained in 
the glands has a deep-brown color, a sticky, niolasses-like consistence, 
a disagreeable, pnngent odor, and a sharp, resinons taste, suggesting 
turpentine or Canada balsam. 

The development of the oil glands seems to be especially great in 
the Egyptian variety knoAvn as Mit Afifi, a;id the glands are more 
superficial. By slight pressure, or by drawing the nail across the sur- 
face, the oily liquid is freely obtained. Most of the Ujiland varieties 
have the oil glands much more scattering and deep set than the Egyp- 
tian sorts, and it is not possible to squeeze the resin out of them in 
any such manner. 

On Redshank and other Upland types the resin glands are marked 
by slight superficial depressions, but a cross section shows them to be 
well below^ the surface, with several layers of chlorophyll-bearing 
cells betw^een. On the Egv^j^tian sorts the glands are also set in de- 
pressions, but the gland itself is very close to the surface, and makes 
the bottom of the depression again convex, the superficial layer of 
cells being very thin. It seems to break spontaneousl}' in some in- 
stances; at least there are frequently small spots of hardened resin, 
and very slight pressure brings out the dark, gummy fluid. The 
fingers receive a permanent brownish stain, which with the acrid, 
biting sensation experienced when the liquid is a{)plied to the tongue, 
increases the probability that substances of a definitely protective 
character are present. It is well known that many of the aromatic 
oils are for some reason highly distasteful or even fatal to many 
insects. 

The Sea Island and Kidney cottons have the oil glands consf)icu- 
ously developed, like the Egyptian varieties, but the Old World 
cotton {Gossyjnum herhaceum) is in this, as well as in other respects, 
more nearly related to the American Upland cotton (Gossypiifm hir- 
svtum). The Aidin (Asia Minor) variety of GoHHypmm herhaceum 
has the oil glands rather small and deep set, with the superficial pits 
rather shallow, more so than the Ceylon or Korean types. 

Even the petals of the Guatemalan Kidney cotton found at Trece 
Aguas '' contained oil glands. The color of the petals was a uniform 
pale yellow, without purple spots on the inside, but in the upper 

a Quaintance, A. L.. and Brues, C. T.. 1905. The Cotton Bollworm, BuL 50, 
Bureau of Entomologj% U. S. Department of Agriculture, p. 71. 

'' The Kidney cotton at Trece Aguas is called iHihi'i. and seems to have little or 
no relation in the minds of the Indians with the dwarf Upland cotton, which is 
called uok. In the Secanquim district, only a few miles away, this name paiyi 
(pronounced like the English words pie ye) is not recognized. Kidney cotton, 
though apparently not now planted by the Indians, is not entirely unknown to 
them. They call it simply cJie nolc, or tree cotton. 



54 WEEVTL-RESISTING ADAPTATIONS OF COTTON. 

half specked with minute brown <ilandiilar dots." The oil glands of 
the bolls of this Kidney cotton are apparently quite as strongly devel- 
oped as in the Egyptian varieties, or even more so. They are distrib 
nted very irregularly over the surface, and are not lacking above the 
dissepiments, along the middle of the carpels. The position aiid 
structure of the glands seem also to be the same as in the Egyptian 
cottons. They are close to the surface and show as distinct black 
spots, there being no green tissues over them as in the Upland and 
herbaceum types. 

I am indebted t-o Mr. Guy N. Collins for the suggestion that the 
present inefficiency of the oil glands as a means of protecting the 
cotton from the boll weevil furnishes no argument against the 
adaptation of the glands nor their development through the selective 
agencies of the boll weevil itself. This fact is sufficiently obvious 
when once stated, but it is not commonly taken into account in con- 
sidering questions of this kind. We may be sure that the gradual 
development of a protective character like the oil gland would carry 
with it a corresponding increase in the power of the weevil to avoid 
or to endure the injury. The ultimate value of the device would de- 
pend on whether the glands were able to keep ahead of the weevils 
in quantity and distastefulness. The readiness with which the boll 
weevils attack the Egyptian cotton renders it obvious that oil is now 
no adequate protection, but the preference of the weevils for the un- 
protected strips of the bolls of the Kekchi cotton indicates that the 
weevils still dislike the oil, though they may have foiled the attempt 
of the plant to protect itself in this way. 

There are two attendant facts which under certain circumstances 
might readily obscure the immunity of the young bolls. Many such 
small bolls fall off, a particularly large number it seemed from our 
row of Parker cotton, but an examination of these failed to show 
anything in the way of weevil injuries, except such as had been in- 
flicted while the bud or flower was still in place, the style and a 
small apical cavity having been eaten away in numerous instances. 
Many small bolls were to all appearances quite uninjured. They 
may have been rejected by the plant as supernumerary, the plant 
being unable to furnish the food material needed to bring them to 
maturity, or they may have failed of fertilization as a result of 
weevil injuries to the bud or from other causes, such as the absence 
of bees, which were extremely scarce in the Guatemalan cotton fields. 
The frequency with which the boll weevils were found inside the 

a The flowers of the Kekchi cotton are inire creamy white when young and as 
long as they remain open. When ohl and rolled together they hecome a pinkish 
red. They are not yellow or bluish at any stage. The stamens and pistils are 
also nearly white, the latter with rows ( f oil glands showing as small grayish 
dots. 



RAPID GROWTH OF YOUNG BOLLS. 55 

cottoji flowci's aixl well diistpd over with pollen sug;gests (lie possi- 
bility that in this district at loast they were a not nnimportant 
agency of cross-fertilization. The ])erforniaiice of snch a service by 
the boll weevil wonld be comparable to the famons case of the yucca 
and its moth, the plant being dependent for cross-fertilization upon 
its insect parasite. The weevils eat the pollen from the bud; that 
they visit the floAvers for the same purpose seems highly j^robable. 
The investigations of Messrs. Hunter and Hinds have shown, indeed, 
that a pollen diet is a necessity for the complete sexual maturity and 
rejjroduction of the weevils; if without buds to feed upon they 
seldom copulated and never laid eggs." 

RAPID (iROWTH OF YOUNG ROLLS. 

Mr. John H. Kinsler, who gave careful attention to the earlier 
stages of the (xuatemalan experiuient, gained an impression that the 
young bolls of the Kekchi cotton increased in size with a rapidity 
distinctly greater than that of the United States Upland varieties 
planted alongside. It was not practicable to establish the fact by 
carrying out a series of daily measurements, though it Avas possible 
to ascertain from dated tags used in connection with the hybridiza- 
tion experiments that the Kekchi cotton can grow^ bolls to full 
size in less than a month from the time the flower opens. Plate IX, 
figure 2, shows on the right two bolls of Kekchi cotton less than a 
month from flowering. On the left are the two largest bolls from an 
adjoining plant of King, the seed of both varieties having been sown 
the same day. 

Such an acceleration of the growth Avould be of very obvious utility 
in lessening the period in which the dangei- of infestation is greatest. 
A large proportion of the weevils found in adult bolls of Kekchi cot- 
ton were in " locks " or compartments of diminutive size, showing 
that the infestation had taken place while the boll was less than half 
grown. Indeed, the weevils seldom seem to be able to affect lodg- 
ment in bolls more than half grown, although numerous attempts 
are made in fields where the weevils are numerous. The following 
field note describes such an instance : 

A holl sliowiiifi many external marks of weevil punctures was found on being 
cut up with care to have been attacked at least fourteen times. In five cases 
the outer wall seemed not to have been iienetrated, but in nine others there had 
been complete perforations. All of these had been closed, however, by prolifer- 
ation from the inner surface, and no living larvje were found. 

Such persistent attacks, however, may finally induce a diseased 
condition which interferes with the normal gi'owth of the boll, even 

" Hunter, W. D., and Hinds. W. E., 190.^>. The Mexican Cotton Boll Weevil, 
Bui. ."tL Bureau of Entomology, U. S. Department of Agriculture, p. 113. 



56 WEEVIL-RESTSTTNG ADAPTATIONS OF COTTON. 

though the weevils be successfully resisted. Such injured bolls often 
show a brownish discoloration of the interior tissues near the base 
and connecting with the nectaries, which may indicate a bacterial 
disease, to be discussed later. Sometimes this ail'ects the walls only, 
sometimes one or more seeds and the surrounding lint. 

THICK-WALLED BOLLS. 

In the Kekchi cotton there are considerable variations in the thick- 
ness of the outer wall of the boll. Not infrequently the wall equals 
or exceeds the length of a weevil's snout, so that only the largest or 
longest snouted weevils would be able to make an opening into the 
interior cavity. It was noted, also, that on the inside such bolls are 
often quite free from these injuries or small larvse, though numerous 
attempts may have been made. Large larva' or pupoe may be found, 
but these have come, obviously, from eggs laid while the boll was still 
young. On some plants the development of large thick walls takes 
place very promptly, so that a protective character of considerable 
value might be obtained if this feature could be increased and ren- 
dered constant. Pearly development of the thick walls Avas indicated 
by the fact that the young seeds and lint did not fill the cavity, and 
the seeds were still far from mature. Instances might be drawn 
from other plants where the growth of the pod or seed vessels far 
outruns the seeds at first, so that the development of such a character 
in cotton might reasonably be expected. 

Even when a wall thicker than usual has been bored through, the 
&gg must be laid on the outside of the mass of lint which still inter- 
venes between it and the young seed, so that the larva's chances of 
development are greatly lessened. As will be shown later in the dis- 
cussion of proliferation in the bolls, the instances are very numerous 
in which, although the wall is penetrated, no further damage results; 
either the egg is not laid or the development of the larva is pre- 
vented by proliferation. In any event the boll escapes further 
injury, and it is a very significant fact that in the dissection of a large 
number of such bolls of Kekclii cott(m scarcely any young larva? 
were found, in spite of the fact that most of them had been punctured 
not once only, but many times. 

TOLTGH LININGS OF CHAMBERS OF BOLLS. 

The three, four, or five chambers which contain the locks of cotton 
in the unopened boll have each a complete membranous lining. In 
the Kekchi cotton, at least, this is extremely tough and parchment- 
like, e^^en in bolls not yet fidl grown and in which the seeds are not 
yet fully formed. This membrane is readily separable from the 
more fleshy external layers of the l:)oll, and though flexible, it is very 



TOUGH LININGS OF CHAMBEKS OF BOLLS. 57 

(ii'iii and incoiiiprcssiblc. aiul resists tcariii*;" unless considerable 
strength be exerted. 

A large percentage of attempted punctures of the larger bolls 
failed because the weevils are unable to penetrate this protective lin- 
ing. This fact is readily determined by the study of radial sections 
of the outer wall through the warts which mark the weevils' points 
of attack. The different texture of the new tissue which has closed the 
wound show\s, usually, that the cavity eaten out by the weevil extended 
down to the tough basal lining, even when no evidence of the injury 
has become apparent on the inside. In other instances, also very fre- 
qnent, the new tissue, develoi)ed as a result of the irritation of the 
attempted pimcture, exceeds the cavity and causes an inward swelling 
or prominence of the inner lining analogous to the projecting warts 
which are the usual external indication of weevil punctures. 

It occasionally happens, too, that the projection of the new tissue 
occurs almost entirely in the inside, the external wart being very 
slightly developed or not at all, though the new tissue and the inner 
swelling show" that a puncture had been attempted. 

The utility of this lining as a means of excluding the boll weevil 
seems not to have been considered heretofore, and there has been no 
opportunity as yet to compare the Kekchi cotton with other varieties 
with regard to this feature." Certain it is, however, that in the Kekchi 
cotton the parchment lining is almost as firm and tough as that which 
surrounds an adult coffee seed. And it is certain, also, that a very 
large proportion of the attempted punctures of the bolls failed to 
bore through this inner wall of defense. 

The examination of a large number of bolls, which were full size or 
nearly so, though still far from maturity, in most cases failed to find 
more than a very few instances, if any, of very recent perforation, 
though there were large nmnbers of instances where the weevils had 
gnaw'ed their way down through the parchment and deposited an 
egg. In many such cases the proliferation or new growth induced by 
the injury causes the parchment to be raised up from the Avail on the 
inside to form a blister- like, rounded protuberance. (PL VIII.) 
Eggs laid outside the parchment are firmly embedded in the new 

" Since this was written Mr. McLachlan has reported the existence of the same 
form of protection in Upland varieties in Texas. The following note describes 
the results of injuries inflicted upon the bolls of a plant of Parker cotton in four 
days from August 8 to August 12, 1905 : 

" The larger bolls, when opened, were found to have 28 weevil eggs deposited 
in them ; C, had struck the dissepiment : 12 were not entirely through the shuck of 
the boll (either not more than half way there or else stuck in the tough inner tis- 
sue of the shuck) ; the others were embedded in the lint. In only two instances 
was there any proliferation apparent. The outer shuck had proliferated at the 
wound and in one case had encysted the egg. The other had merely forced the 
egg to one side, having begun the development too late." 



58 WEEVTI^-RESISTTNG ADAPTATTOXP OF COTTON. 

growth and do not appear to hatch, or if tliey do the hirva- are not 
able to do any damage, since they can not penetrate into the interior 
of the bolL It (juite freciiiently haj)j)ens that eggs are laid in the 
^iniLs or groove between the linings of two locks, but without penetrat- 
ing the parchment of either. The tissue is here somewdiat looser 
than in other parts of the wall. In a few instances it was observed 
that the larva^ had hatched, but no case was found which indicated 
that larva^ hatched outside the parchment lining had been able to 
penetrate to the interior cavity. 

PROLIFERATION FROM THE WALL OF THE BOLL. 

The w^all of the boll offers an active form of weevil resistance by 
proliferation, in a manner somewhat analogous to that of the pro- 
liferation of the square. The channel excavated by the weevil is 
closed by the new growth, wdiich continues to push out on the inner 
surface of the wall in llic form of a rounded, blister-like protuber- 
ance of loose tissue. This surrounds and encysts the weevil egg, and 
prevents its development. A section through the mass of new tissue 
shows the egg embedded in it or pressed against the lint. Prolifera- 
tion often takes place even when the tough lining of the chamber has 
not been penetrated, and then appears as a prominence underneath 
the membrane. 

It has been seen from the preceding paragraph describing the 
thick walls and tough lining that in the Kekchi cotton, at least, 
the weevil is practically excluded from the boll after the boll has 
reached about three-quarters of its full size; but even in its younger 
stages also there is a measure of defense through the formation of 
new tissue as a result of the irritation set uj) by the weevil's injuries 
in a manner analogous to that which induces the formation of galls 
and other vegetable excrescences. 

The first result of the proliferation is to fill up and heal the 
wound bored out b}^ the weevil. The cavity is not only completely 
filled, but in most cases a wartlike prominence is formed on the out- 
side, and if the parchment lining or the inner wall has been pene- 
trated the new j^roliferating tissue also grows through on the inside 
and often spreads out as a biscuit or button shajied protuberance 
of soft white or transparent tissue several millimeters in diameter 
and readily visible to the naked eye. (PI. VIII.) 

There are two alternatives in the fate of an egg destroyed by 
proliferation. Either it is completely surrounded in the proliferating 
tissue outside or inside of the parchment wall or it is carried on 
the apex of the proliferation down against the lint and flattened 
between the growing surfaces. After the egg has disintegrated 
and disappeared its position is frequently shown by a minute brown 



PROLIFETtATTON FBOM WALL OF BOLL, 5V) 

stain. Such a discoloi-atioii often jspreuds back into the loose tissue 
and then gradually extends over the whole lock of cotton of that 
particular chamber. The seeds fail to develop and tinally shrivel up. 

If the proliferation results, as usual, in the death of the weevil 
egg or young larva, the process of abnormal growth ceases with 
the formation of a knob or button of the new tissue on the inside 
of the Avail of the boll. When, however, the young weevil escapes 
destruction and continues to eat and grow, the proliferating tissue 
also continues to increase, until in some instances the whole compart- 
ment is filled with a silvery-white cheesy material which seems to 
arise not only from about the original perforation of the outer wall, 
but also from other ]:>arts which have been injured and irritated 
by the presence of the weevil larva. This, with other facts already 
stated, seems to show that in some varieties of cotton, at least, the 
tendency to proliferation is very general, or, in other words, con- 
stitutional, which warrants a larger hope of increasing this character 
and making it uniform by selection. 

'WTien proliferation, which results from the presence of the weevil 
larva, has become very extensive and fills the entire compartment, 
the weevil larva is sometimes found to have eaten through the dis- 
sepiment into the next chamber, perhaps to escape starvation. Such 
extensive proliferation, accompanied by the failure of the seeds to 
develop, means, of course, that the weevils gained entrance while the 
boll was still very young. Moreover, if the boll had been older 
there would have been plenty of food for the larva without the 
necessity of entering a second compartment. Finally, the dissepi- 
ment would have been too tough for the larva to penetrate easily. 

Further proof of the fact that the weevil larva^ are seldom or 
never able to gain a footing in the larger bolls is to be found in the 
fact, already stated, that the weevil larva^ found in them are nearly 
always in undersized compartments, much smaller than those which 
have remained uninjured, and have thus been able to continue their 
normal development. 

It is to be supposed, perhaps, that if the weevils could gain access 
to large bolls and feed upon the nearly adult seed they would be able 
to develop in less time than they usually spend in reaching maturity 
on the rather poor provender they secure among the abnormal tis- 
sues which arise after they have entered the young bolls. 

The exclusion of the weevil from the large bolls has been evidently 
not only an important measure of protection for the cotton, but it 
has probably compelled the weevil to accustom itself to a gradually 
longer and less prosperous development in the boll. The develop- 
ment of the weevil-resisting adaptations on the part of the cotton 
plant has left the insect Avith two opposite alternatives. It must 
enter the boll early and submit to a very long period of development 



60 weevil-reststtnot adaptattonr of cotton. 

or filter the s(iiiare late and develop very promptly. The insect has 
been able, as we know, to avail itself with a hir<>e measure of success 
of both these alternatives, but it is not without encouragement for 
future progress in weevil resistance to know that the plant has so 
successfully guarded itself in two parts of its life history. 

If additional evidence be needed to show that the food supply 
obtained by the weevil larvse in the bolls is very dilferent from that 
in the squares, it is to be found in the large, firm-walled cells of com- 
pacted excrement with which they surround themselves in the bolls 
before reaching maturity. The food being of a much coarser nature 
and the period of development about three times as long, the amount 
of waste material is naturally very much greater. If feeding upon 
the boll is, as now^ appears probable, the ancestral habit of the wee- 
vil, it need not surprise us that the protective adaptations of the boll 
are more numerous and effective than those of the bud, which maj' 
have been attacked by the weevil in comparatively recent times. 

TIME REQUIRED FOR PROLIFERATION. 

In connection with the experiments in Texas, Mr. McLachlan at- 
tempted to ascertain the time required for proliferation to take place 
after the injury had been inflicted. The amount of proliferation 
and the time required for it to develop ma}^ be expected to depend 
much on external conditions. Squares of Parker cotton showed no 
development in six hours, but observation on bolls showed that pro- 
liferation w'as complete in twenty-four hours. Two of Mr. McLach- 
lan "s observations are described in the following notes : 

Ou August 14, at 0.15 a. m., a wii'e cage was placed over a plant of King 
cotton, and four weevils, of which at least two were females, were put inside. 
Later, three more were introduced. At the time there were 11 bolls, 39 squares, 
and 1 flower on the plant. 

On August 17, at 1 p. m., 11 bolls and 18 squares were picked, a little more 
than three days being allowed for the weevils to work. There was no rain, and 
of the 18 squares examined only one revealed proliferated tissue, though the 
weevils had scarred the buds in more th.ui .S3 sei)arate places and had deposited 15 
eggs. But the bolls showed better results. They had been scarred at 32 different 
points, and 23 eggs were discovered when the bolls were exit oi)en. In 12 cases 
inward proliferation of the " shuck " had destroyed the eggs. Several of the 
incited growths had caught the egg, encysted it, and carried it along, inclosed 
at the apex, as they pushed their way into the lint. As in the Parker cotton 
examined a short time ago, weevils seem to have some difficulty in getting 
the egg through the shuck of the boll. In dry weather it appears that the 
King cotton is as backward as the Parker in proliferation in the squares, but 
in bolls proliferation goes forward as well in dry as in wet weather. 

On the 30th of August, at 10.15 a. m., a boll (half grown and tender) was 
bagged with a weevil. At p. m. of the same day an egg puncture was found 
on the fruit, but at 8 a. m. of the 31st no further injury had been inflicted. At 
12 m., September 1, four more egg ininctures were discovered, and the boll was 



EFFICIKNOV OF ADAPTIVE CHARACTERS OF EOLLS. <i 1 

piilk'd luul exiiniined. Tlie tirst puncture was then forty-two hours old and ihe 
other four some twenty-four hours old. The examination revealed marked pro- 
liferation in every case, with no greater growth in that of forty-two hours" 
duration than there was in tliat of twenty-four. Eggs had been laid inside the 
wall of the holl, since it was easy, in the case of young, tender fruit, for the 
weevil to cut an opening to the lint. But every one of the five eggs had been 
encysted by the proliferated tissue. It is (luite possible that one or two of the 
punctures reckoned as twenty-four hours old were still more recent. 

EFFICIENCY OF ADAPTIVE CHARACTERS OF BOLLS. 

The amount of protection afforded in Guatemala by the weevil- 
resisting characters of the bolls might be greatly underestimated if 
it were to be supposed that the weevils make numerous attacks upon 
the bolls for the purpose of feeding upon them. 

In their accounts of the habits of the boll weevil in Texas, Messrs. 
Hunter and Hinds have devoted a chapter to " effects of feeding upon 
squares and bolls,"" but in Guatemala no indications were found that 
weevils punctured the larger bolls for any other purpose than egg 
laying. It is true that the outer surfaces of bolls are frecpiently 
marked with scars of weevil punctures from which no larva' have 
developed and no internal injuries have resulted, but these failures 
can be explained in other ways than by the supposition that the wee- 
vils feed upon the tough and innutritious outer walls of the bolls. 
In Guatemala, at least, it appears that the weevil scars on large bolls 
mark attempts at egg laying, though for a variety of reasons already 
recited most of them are not effective. The only instance where wee- 
vils were found feeding in bolls in Guatemala was at Rabinal. Two 
weevils were together attacking a small l)()ll, and had eaten out large 
superficial pits, quite unlike the punctures in which eggs are laid. 

Feeding punctures in bolls are referred to by Mr. McLachlan in a 
note dated at Victoria, Tex., August 31, 1!)05. Such injuries were 
not found, however, to lead to the formation of external warts which 
could be mistaken for egg punctures, doubtless for the reason which 
Mr. McLachlan gives : 

It has been noticed that in bolls no proliferation occurs following the injury 
from a feeding puncture, liowever serious tliat may be. Furthermore, from the 
above and other observations it is apparent tliat proliferation is not excited by 
the egg puncture or the egg, unless the puncture extends tlirough the inside 
tissue and the egg is fixed in the tissue or has been puslied through it to the 
lint. In that case a dense knob of proliferation occurs on the inner side of the 
shuck, in the center of which the egg is often encysted. There must be a con- 
stant irritant like tlie egg, with an opening to give it access to the lint, in order 
to occasion the specialized growth. As a suggestion it might be noted that all 
the egg punctures are sealed by the adult weevil at the time of egg laying, 
while the feeding punctures are left open. 



"Hunter, W. D., and Hinds. W. E., 1905. The Mexican Cotton Boll Weevil, 
Bui. 51, Bureau of Entomology, U. S. Department of Agriculture, p. 59, PI. VIII, 



62 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

The feeding experiment reported by Messrs. Hunter and Hinds " 
shoAvs that weevils fed exchisively upon bolls lived less than twenty 
days, Avhile those fed upon the squares lived nearly seventy days. 
The bolls j)roved to be much less suitable for food than the leaves, on 
which the weevils were able to prolong life for thirty days and 
u.pward, though no eggs were laid on a leaf diet. It may be that in 
Texas, where the army worms sometimes destroy all the leaves, the 
weevils might be driven to gnawing the bolls for food, but in Guate- 
mala the plants remain in full leaf throughout the gi-owing season. 

BACTERIAL DISEASES FOLLOWING AVEEVIL INJURIES. 

In the study of the bolls of the Kekchi cotton three diseased con- 
ditions were observed, some or all of which may be of bacterial 
origin, the bacteria having been introduced, perhaps, by the weevils 
at the time of egg laying. None of these diseased conditions is fre- 
quent, and as they do not i3ermit the fruit to reach normal maturity 
it seems very unlikely that they can be introduced into the United 
States with the seeds. It may be stated in addition that the seed 
obtained by Mr. Kinsler in the season of 1905 has been carefully 
selected in the field and comes from the earliest and most vigorous 
bolls. 

The first of the diseased conditions consists in a white deliquescence 
of the immature seeds and lint as though the lock had been dipped in 
milk. There is also a distinct odor of fermentation. Another dis- 
ease turns the seed and lint brown. Though observed only in bolls 
which have been punctured by the weevil, there was often an 
apparent connection l^etween the disease inside and the large extra - 
floral nectaries. A column of transparent or somewhat discolored 
tissue extends from each nectary obliquely upward to the cavity of 
the boll. This may be a symptom of the disease or it may indicate 
that bacteria find their way into the bolls by Avay of the nectaries. 

The third abnormal condition was also indicated by a brown dis^ 
coloration of the wall and contents of the atfected compartment of 
the boll. The seeds and lint soon die and shrivel. No special indi- 
cation of bacterial activity was noted, and it may be that the death 
of the weevil egg or larva has some prejudicial eft'ect upon the sur- 
rounding cells, as suggested by the brown discoloration already 
noted in describing the effects of proliferation. Such a distvu-bance 
might continue to spread and thus cause the death of the young seeds. 

BREEDING IN BUDS A DERIVED HABIT. 

The fact that the weevil larva- are found in the young buds of the 
cotton plant and also in the full-grown bolls has been taken to mean 
that it affects all the intervening stages as well. This would imply 

« Hunter, W. D., and Hinds, W. E., 1. c, pp. 34-35. 



BREEDING IN BUDS A DERIVED HABIT. 63 

also that if the weevil fed originally upon the bolls it has followed 
back to earlier and earlier stages and finally to the bud. The facts 
already detailed seem to prove, however, that this is not the case. 
The weevil does not attack the very young bolls, nor does it operate 
Avhile the flower is open or while it remains in place, though in a 
Avithered condition. The hatching of the weevil larva in the large 
buds is likewise ineffective because the larva is deprived of shelter 
when the flower opens. It seems necessary to believe, therefore, that 
the parasitism of the weevils upon the buds of the cotton is a habit 
quite distinct from that of its relations to the boll. The habit of 
breeding in the bud marked a ncAv departure in the biological history 
of the insect and not a gradual change from the previous habit of 
infesting the bolls only. Nevertheless, the change of habits need not 
be thought of as anything very remarkable from the standpoint of the 
insect. A cotton bud is very much larger than a small boll. The 
peculiarity lies in the plant rather than in the insect, since ^ery few 
plants afford a continuous and abundant succession of large, pollen- 
filled buds. It is this quality of the cotton plant which has enabled 
the weevil to develop its peculiar and highly destructive secondary 
habits of feeding upon the buds and using them as breeding places. 
If the boll weevil were restricted, like related beetles, to parasitism 
upon the fruit of the cotton, it would have remained a comparatively 
harmless and agriculturally insignificant enemy. These considera- 
tions may assist in a better appreciation of the extent to which the 
weeviFs power of injury would be diminished if we could obtain a 
variety of cotton with a fully determinate habit of growth, one which 
would cease producing buds as soon as a crop of cotton had been set. 
The much more rapid development of weevil larva' in the bud is 
to be connected, doubtless, Avith the much richer food offered by the 
mass of pollen, but it may represent also a somewhat more definitely 
adaptive specialization of the life history of the weevil, for it is gen- 
erally a question of eating the pollen promptly or not at all. If the 
bud falls off on moist groimd the i)ollen would be completely decom- 
posed long before the lar\'a could develop, at the rate at which it 
grows in the boll, and if the bud did not drop off', but continued to 
grow, the flower would open and turn the larva out. It is obliged, 
therefore, to do damage fast enough to keep the flower from opening, 
and must then eat the remaining pollen before it spoils and leaves 
the larva too hungry and stunted to pass through the final meta- 
morphosis into the adult stage. In a cotton which has a highly 
developed habit of shedding the injured buds it would not be so neces- 
sary for the larva to attack the pistil. It may be that this policy 
on the part of the weevils in Guatemala has a use to the weevil as 
being necessary to prevent the opening of the flower and cause the 
falling of the bud. 



64 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

The tliviTsitv in size of the 1)()11 weevils, while not nnprecedented 
among insects, is nniisual, and not withont biological significance in 
the present connection. An explanation of the variation in size is 
to be found, no doubt, in the varying amounts of food which the 
weevil larva? can obtain, but there is needed, none the less, a special 
adaptability on the part of the weevil to permit it to reach a normal 
reproductive maturity in spite of very unfavorable conditions. The 
smaller weevils probably have less than a quarter of the weight of 
the large ones, which means that thej' are able to develop with a cor- 
respondingly small proportion of the food required to raise a full- 
sized weevil. The weevils developed in the bolls have a much greater 
uniformity of size. The small weevils are at once a means and a 
result of the acquisition of the habit of living in the buds, and espe- 
cially in the small ones, where the supply of food is often very small. 

RELATION BETWEEN PROLIFERATION IN BUDS AND IN BOLLS. 

The analogy of the mucilaginous tissue found in the young fruits 
of okra and other relatives of the cotton would lead us to expect that 
proliferation could occur more readily in the boll than in the bud, 
Avhicli may mean that all the varieties which proliferate in the bud 
will do so in the bolls as well. 

It was at first supposed that if the buds proliferated but not the 
bolls the result would be merely a postponement of the breeding 
season of the weevil for two or three weeks, or until the bolls had time 
to develop. Such a delay would be of great practical imi^ortance in 
retarding for that length of time the elective breeding period of the 
w^eevils. Moreover, most of the eggs of the weevils which had passed 
through hibernation would be lost by being laid in the buds, which 
would further keep down numbers in the early part of the season. 
There is, hoAvever, the further and still more important consideration, 
that the period of development of the Aveevil in the boll is very much 
longer than required for it to mature and emerge from the square." 

« Determinations of tlie lengtli of the life cycle in bolls have been made only 
in a few instances. In 7 cases between August 15 and November 11, 1903, 
the average time required from the deposition of the egg to the escai)e of the 
adult from the opening boll was sixty-one days. The average effective tempera- 
ture for the period was .'>1.7° F.. and the average total effective temi)erature 
retiuired for development in bolls was therefore 1,933.7° V., or nearly two and 
one-half times as much as in sciuares. Several larvie often develop within a 
single boll. They appear to remain in the larval stage until the boll l)ecomes 
sutticiently mature or so severely injured as to begin to dry and crack open. 
When this condition of the boll is reached, pupation takes place, and by the 
time the spreading of the carpels is sufficient to permit the escape of the weevils 
they have become adult. — Hunter, W. D.. and Hinds. W. E., The Mexican Cotton 
Boll Weevil, Bui. 45, Division of Entomology, U. S. Dept. of Agriculture, 1904, 
p. 75. 



PROTECTION OF SEEDS BY LINT. 65 

Moreov'er, it seems that the adult weevil does not come out through 
the wall of the boll, but waits to be liberated when the boll opens to 
maturity. This would mean that if proliferation can exclude the 
weevil from breeding in the squares it would afford a practical solu- 
tion of the problem, since instead of merely delaying the emergence 
of the first brood of weevils for two or three weeks, none of them 
would be able to set about the work of destruction until the crop had 
begun to ripen, and all danger of appreciable damage would have 
passed. It seems, therefore, that the proliferation in the squares is 
the much more valuable characteristic to be considered in seeking for 
a weevil-resistant cotton. Proliferation in the bolls is very desirable, 
but the absence of it should not be allowed to figure very largely 
against a variety which might have a pronounced tendency tow^ard 
proliferation in the bud. Nevertheless, other factors must enter the 
calculation, for thin-walled bolls might allow the weevils to escape 
earlier. In moist weather the bolls might not crack open, but give the 
weevils comfortable shelter all winter, as would seem to have been the 
case in the spring of 1905, when various observers noted that some of 
the weevils seemed to have the appearance of having emerged only 
recently from the piipal condition, their very light color showing that 
their outer covering of scales Avas still in place. 

The probability is, however, that the proliferation in both places , 
will be found to depend upon the same internal factor or quality, 
so that it will be safe to assume that a high degree of proliferation 
in the bud could be taken as an index of what might be expected 
from the bolls. This would simplify the problem of selection by 
permitting us to confine our attention to the buds. 

PROTECTION OF SEEDS BY LINT. 

Like the large leafy involucre, the lint is also a peculiar feature 
of the cotton plant which may prove to have a practical connection 
with the weevil. Cotton is the only food plant of the boll weevil, 
and only the cotton, of all the related plants, has an abundant pro- 
vision of lint. Some of the species of Hibiscus have the seeds 
slightly silky, but the cotton stands quite alone in the length and 
abundance of the hairy covering which grows out from the seeds at 
(he time the bolls are most subject to weevil injuries. 

From the standpoint of those who believe that all characters are 
useful to the organisms which possess them, the interpretation of the 
lint as a weevil-resisting adaptation will not appear unreasonable, 
since it can scarcely be claimed that there is any other use of the lint 
so important to the ]:)lant as j)rotection of the seeds from the weevils. 
In other respects the lint seems rather a disadvantage than other- 
99()1!— No. SS — K)Ti M 5 



66 AVEEVIL-RESISTING ADAPTATIONS OF COTTON. 

Avise. In a humid tropical country the seeds, if left to themselves, 
remain inclosed in the tangled mass of lint and usualh' rot. Birds 
might carry the lint away to build nests, and in so doing might assist 
in scattering the seeds, but in most of the varieties the seeds are to 
be detached only with difficulty. 

Composed as it is of nearly pure cellulose, the lint can aiford very 
little nourishment, even in the younger stages. Between the lint and 
the watery proliferating tissue the weevil larva must find the inside 
of a cotton boll a very inhospitable place unless it can penetrate to the 
seeds. Dead and moribund larvte are occasionally found in these 
unfavorable situations. And even the seeds themselves do not pro- 
vide so favorable a food as the pollen, as shown by the nmch longer 
tmie required by the larva- to develop in the boll than in the sc^uare. 

PROTECTIVJ: seed arrangement in kidney rOTTON. 

Further intimation of the protective value of the lint is to be found 
in the very peculiar Kidney cottons, so called l)ecause the seeds are 
crowded together in the central angle of the chaml)er and adhere 
firmly to each other, thus forming a small, kidney-like mass. This 
unique arrangement brings all the lint to the outside of the seed, and 
may be the explanation of the fact that the Kidney cottons are the 
only representatives of the Sea Island tyix> which have gained a wide 
distribution on the mainland. The separate-seeded Sea Island cot- 
tons came from Barbados, where the boll weevil did not exist and has 
not yet been introduced. (See PI. X, fig. 2.) 

The outer wall of the boll of the Kidney cotton is notably thinner 
than that of Kekchi cotton, so that the beaks of the weevils could 
reach through without difficulty. But with the layer of lint to sup- 
plement it the wall becomes, for practical purposes, much thicker than 
in the free-seeded varieties. The inner parchment lining is rather 
tough, though ap])arently less so than in the Kekchi cotton. 

The Indians about Trece Aguas, Guatemala, are said to recognize 
the weevils as enemies of the dwarf cotton, but it is the local opinion 
that the Kidney cotton is proof against them. 

No weevils Avere found on the two bushes of Kidney cotton exam- 
ined in that locality, but these w'ere single plants growdng near Indian 
houses several miles away from the nearest field culture. In a forest- 
covered country like this part of Guatemala the luxuriant and 
tangled vegetation may Avell impede the flight of such an insect as the 
Aveevil. And if it lives, as supposed, only on cotton, its chance of 
}-eaching a single bush of tree cotton would be very small. That the 
buds and young bolls of the Kidney cotton are able to offer any abso- 
lute resistance to the -weevil seems very imi)robable, and the abundance 
of weevils found on the large tree of Kidney cotton at Tucuru last 
year proved that the immunity, if an3% is not general. 



NATURE AND CAUSES OF ADAPTATIONS. (i7 

The Kidney cotton, though commonly treated as a distinct species 
under the name Gossypuim peruvianum, agrees with the Sea Island 
type in all its characters except the peculiar arrangement of the seeds. 
If this should prove to be an adaptive feature the idea of specific 
distinctness would have little left to support it. 

CULTURAL VALUE OF KIDNEY COTTON. 

The possession by the Kidney cotton of a definite weevil-resisting 
adaptation would naturally raise a question regarding its cultural 
Aalue. It belongs to the Sea Island series, and has the long, fine fiber 
and smooth seeds. The growing of the seeds together in masses would 
still further facilitate picking and ginning operations. The bolls, too, 
of this Guatemalan Kidney cotton, at least, are larger than those of 
any of the Sea Island varieties. 

It is not likely, however, that any of the varieties of Kidney cotton 
thus far known will l)e found of use in the United States, for all are 
perennial '' tree cottons." which have refused thus far to flower or 
fruit in the period of growth allowed by the shorter summers of our 
Temperate Zone. In tropical regions this objection would not hold, 
and there appears to V)e no reason why the Kidney cottons shoidd be 
disregarded in the search for varieties suited to the various soils and 
climates. The Trece Aguas Kidney cotton, for example, seems to 
thrive well in a humid mountain climate considered by the natives to 
be unfavorable for the annual Kekchi cotton, which is planted several 
liundred feet lower down. 

THE NATURE AND CAUSES OF ADAPTATIONS. 

To explain how such characters as the weevil-resisting adaptations 
arise invoh'es an interpretation of general evolutionary questions upon 
which the scientific world is still by no means agreed. Nevertheless, it 
is evident that students of such subjects should conduct and describe 
their investigations in accordance with some consistent plan or 
policy, if th.eir writings are to be understood or their facts intelligibly 
recorded. Moreover, it would be scarcely reasonable to maintain that 
such characters can be further increased by selective influence unless 
it could be believed that they had been assisted in the past by the same 
agency. 

It seems necessary to state that in the present report it is not 
assumed that the weevil-resisting characters have arisen as direct pro- 
tective responses to the injuries, or that they are the results merely of 
stimulation or irritation caused by the weevils, as other writers on 
evolutionary subjects might hold. Nor have they been thought of as 
caused by selection in any strict sense of the word. Though consti- 
tuting a most striking instance of the results of selective influence, it 



68 WEEVIL-KESLSTING ADAPTATIONS OF COTTON. 

is believed that the cotton phmt must first have originated in some 
measure the protective characters before the external conditions (in 
this instance, the Aveevils) could make them of advantage to the 
plants and thus encourage their further development. 

The older theory that environment and natural selection are the 
efficient or actuating causes of evolutionary change has lost many 
adherents in the last decade, especially among those who found 
themselves unable to credit any longer the idea that all the characters 
and differences of i)lants and animals are, or have been, of use to 
them. It has been shown, too, by Professor AVeissman and his fol- 
lowers, that direct adaptations or responses of individual organisms 
to the environment are seldom or nevei' inherited by their offspring. 
To take the ])lace of the doctrine of direct environmental influence 
in evolution it has been suggested that there may be an internal 
'' hereditai-y mechanism."' as it has been called, which determines 
adult characters in advance, in the reproductive cells, so that modifi- 
cations of the specific or varietal type can arise suddenly. Selection 
would determine, of course, wdiich of such new ''mutations" should 
survive, but it Avould be a mere accidental coincidence if the new 
character happened to fit the conditions better than the old. 

It is possible, however, to explain evolutionary progress and select- 
ive adaptations without ascribing them either to external causes or 
to theoretical internal mechanisms. The diversity which plants or 
animals of the same parentage often show under the same conditions 
makes it evident that there is no j)recise mechanism which determines 
their form in advance, and all attempts at securing any absolute uni- 
formity or "' fixity " of form and color have failed. The fact is that 
organisms, even of the same species or variety, are normally diverse, 
and must have ancestry mixed by interbreeding if bodily vigor is to be 
maintained for any great number of generations. 

The generalized "" specific type,'" which is a ])roduct, as it were, of 
this diversity and interbreeding, is constantly and gradually chang- 
ing, and in many Avays at once, though in some characters more rap- 
idly than in others. Selection, while in no strict sense a cause of 
this vital motion of the species or variety, may profoundly influence 
the direction and rate of change. Selection, in other Avords, explains 
adaptation, but does not explain evolution." 

The word adaptation is used in more than one sense by writers on 
biological subjects. Some treat as adaptations the changes of form 
or structure by which many plants and animals are able to conform 
to the needs of different conditions. There are several plants, for 
example, which have nornuil broad leaves when they grow on land, 
and very narroAv and nuich-divided leaves when they grow submerged 

"Natural .Selection in Kinetic Evolution, Science, N. S., 19:549. 1904. 



NATURE. AND CAUSES OF ADAPTATIONS. 69 

in Avatcr. Some plants arc haii'v in dry localities, but arc nearly 
naked in humid districts. Others treat these direct responses to 
external conditions under the heading of accommodation, and reserve 
the word adaptation for characters which appear regularly in a spe- 
cies or variety, but which fit it for some special condition, such as 
that presented to the cotton plant by the boll weevil. It has seemed 
j^roper, therefore, to discuss as protective adaptations any characters 
which seem to give the Central American varieties an advantage in 
withstanding the attacks of the weevil, particularly if it can be shown 
also that the presence of the weevil would tend to the preservation 
and extension of the given character. 

In the strict sense of the words, the weevil-resisting ada])tations 
of the cotton plant would include only those characters which have 
been increased by the selective influence of the boll weevil, but in the 
broader practical sense we may treat as a weevil-resisting ada])tation 
any feature which tends to limit the destructiveness of the insect. 

The adaptive nature of some of the characters of the Central 
American varieties discussed in the present paper is reasonably obvi- 
ous, but in other instances extended studies in developmentaTbiology 
and primitive agriculture might be necessary to determine the origin 
and development of a varietal characteristic which may have signifi- 
cance in the weevil problem. 

It is easy to understand that so injurious an insect as the boll weevil 
has exerted a definite selective influence ever since its remote ances- 
tors turned their attention to the cotton. Perhaps its earlier food 
plants were completely exterminated. The nearest living relatives 
of the cotton are the species of Hibiscus, Paritium, and Thespesia, 
none of which is known to have any attractions for the weevil. It is 
evident, too, that in the presence of the weevil the cotton plant would 
have met long ago a like fate if it had not been able to take on its 
various adaptive characters. That so many of the features by which 
it differs from its nearest relatives have such obvious connection with 
the weevil would certainly justify the belief that strong adaptive 
influence had been at work, even if the other circumstances were 
unknown. 

In thinking of the relation between two organisms like the weevil 
and the cotton we often fall into the error of too great humanizing, 
so to speak ; that is, we ascribe too great intelligence or too complete 
a reaction to cause or conditions. Thus the weevil, although highly 
specialized in some of its instincts, has, of course, no equivalent for 
the human judgment. It will puncture, as already seen, buds much 
too small to raise a larva, and will lay its eggs in the rind of the boll, 
where the larva' can never develop. If the conditions are too favor- 
able to the weevil, as in humid regions, it would undoubtedlv exter- 



70 WEEVIL- RESTRTTNG ADAPTATTONR OF COTTON. 

niinate its own host ])liiiit l>y jx'riiiittiiiij;" the cotton to [)roduc(' no 
seed. Paradoxical as it may at first seem, we may. nevertlieless, 
believe that the best conditions for the per})et nation of the weevil are 
those Avhich are not altogether favorable to its unlimited multi- 
plication. 

CONSCIOUS AND UNCONSCIOUS SELECTION. 

There are two principal ways in which improved varieties of cotton 
and other cultivated plants come into existence. The first is by sud- 
den or abrupt changes, or sports; also called mutations, saltations, 
and discontinuous variations. These are represented in cotton by the 
occasional appearance of a plant with brown lint." deeply divided 
leaves'* (okra cotton) or very short branches (cluster cotton). The 
Guatemalan varieties represent a second type of evolutionary history, 
in which improvement is accomplished by more gradual prorgressive 
change, fostered and accelerated by selection. 

Two forms of selection are commonly recognized, natural and arti- 
ficial, the latter eifected by man, the former by circumstances of the 
enviromnent. This distinction is of doubtful value in any case, and 
quite obscures the important point in the evolutionary history of 
cotton and other plants domesticated by primitive man. It would 
be much better to think of selection as either conscious or unconscious, 
and between these two a very practicable difference exists. Conscious 
selection implies the preservation of individuals having a desired 
quality in the highest degree, while unconscious selection, whether 
by man, animals, or inanimate conditions, means nierely the rejec- 
tion of the most unfit, so that the improvement of the species or 
variety is gradual. Conscious selection acts, of course, much more 

o In Guatemala several tribes of Indians prefer brown cotton, and for certain 
garments use brown cotton only. Sei)arate plantings of brown cotton are not 
made in the neighborhood of Secanquim, where our experiment was located, but 
there were said to be such at Cajabon and Lanquin, only a few leagues away. 
The Cajabon people have a dark -brown cotton called " canch nok," and a lighter 
brown called " canni nok." 

On the Pacific slope Mr. William R. Maxon found considerable culture of a 
brown cotton called " ixcaco." At Antigua a similar brown variety is said to 
have been grown formerly in considerable quantities, the conmion name of 
which is " cuyuscate." It was not learned tliat any special religious use or 
significance is attached to brown cotton in Guatemala, as is said to be the case 
in Peru and in India. 

t> Some may be inclined to interpret these as reversions and to argue that the 
deeply divided involucral leaves may be a reminiscence of an ancestral charac- 
ter of the cotton. Or it may be that the divisions attained by the involucral 
leaves represent a tendency of specialization which the remainder of the leaves 
sometimes share by mutation, in accordance with the principle of translocation 
of characters recently formulated by Dr. R. G. Leavitt (Contrib. Ames Bot.- 
Lab. No. 3). 



CONSCIOUS AND ITNCONSCIOUS SELECTION. 71 

s})eedily than uiicouscious. but is suhjecl to the srrious danger of 
weakening" its proteges l)v inbreeding, if the selection be too rigid and 
persistent. 

The unconscious selection by Avhich the development of the pro- 
tective characters of the Guatemalan types of cotton has been encour- 
iiged differs in no respect from the progress by which adaptive 
evolution takes place in nature. The Indians have planted and har- 
vested the crop, it is true, instead of the birds or other natural agents, 
but they have been entirely unconscious of the struggle for existence 
to which the cotton plant was being subjected by the presence of the 
boll weevil. The Indians were only another factor, along with the 
dry and moist climates, the keleps, and the turkeys. The problem 
has been solved in a genuinely natural fashion, and affords an excel- 
lent illustration of the nature of selective influence in evolution. 

Instead of representing the final possibilities of improvement 
in characters which give protection against the boll weevil, the 
Indian varieties of cotton may be looked upon rather as affording 
materials which conscious selection can render still more valuable. 
The proliferation character, for example, might never be brought to 
uniform expression by unconscious selection, because the possession 
of it would give the individual plant no advantage over its neighl)ors 
in the production of seed. The i)rolif crating plant might produce 
no weevils itself, but the free movement of the insects would keep the 
general average the same. Indeed, a plant uiight easily sacrifice all 
its buds, set no fruit at all, and thus fail to perpetuate itself. Pro- 
liferation can become a direct advantage to the individual plant oidy 
under conscious selection. The full value of the newly ascertained 
protective adaptations will not be known until they have had the 
direct selective encouragement now commonly accorded to desirable 
characters of other cultivated plants. 

It may appear remarkable that such definite and potentially valu- 
able characters as the weevil-resisting adaptations of the Kekchi cot- 
ton should have remained so completely unrecognized hitherto. The 
explanation of this doubtless lies in the fact that cotton culture is 
practiced in Central America largely by the Indians and very little 
by the foreigners or the more intelligent part of the native community, 
so that it had not received scientific study. Even the existence and 
utility of the keleps, though apparently known to the Indians from 
ancient times, had entirely escaped the attention of the European 
residents of the country. That the Indians should have come to 
recognize the keleps as l^eneficial and necessary to a full crop of cotton, 
although not knowing that the weevils injure the cotton or that the 
keleps eat the weevils, only shows in higher relief the completely 
unconscious character of the selection conducted in this system of 
primitive agriculture. The Indians of Alta Vera Paz are extremely 



72 WKEVTL-RESIRTINO ADAPTATTOKS OF COTTOX. 

stolid, nnconiiiiuuicative people, fi-om whom little inforination is 
likely to be obtained except as replies to direct questions. Familiar 
from their earliest childhood with the agricultural lore of their own 
tribe, it does not occur to them that these everyday incidents can he 
of interest to the white stranger, or if they perceive his interest they 
learned long since to fear it as a danger of further intrusion. Even 
our own cotton experiments Avere misunderstood as a menace of addi- 
tional demands for lands from the white men who now own so large 
a part of the country. 

SUMMARY OF ADAPTATIONS. 

If the facts stated in the present report have been correctly observed 
and interpreted, Ave must admit that the cotton plant is in a high 
state of adaptive specialization in its relations Avith its noAv famous 
insect enemy, the boll Aveevil. Indeed, it may be that the most dis- 
tinctive and important characters of the plant, from both the botan- 
ical and the agricultural standpoints — such as the iuA^olucre, the 
nectaries, the oil glands, the large bolls, and the very lint itself — 
are adaptiA^e features Avhich the selectiA^e influence of the Aveevil has 
brought to their present degree of deA^elopment. 

CLA8SIFICATIOX OF ADAPTATIONS. 

The adaptations of the cotton plant might be summarized from 
three different standpoints. A historical treatment Avould proceed 
from the adaptations of the bolls to those of the buds. Breeding in 
the buds, for instance, was evidently a later adaptation on the part 
of the AveeA'ils Avhich has called for a second set of the protectiA'^e 
characters on the part of the plant. 

It may be better, hoAvcATr, to classify the adaptations as such, 
Avithout special regard to their historical sequence of derivation. 
The more practical purposes are serA^ed by dividing the adaptations 
into four groups: (1) Those calculated to aA^oid the Aveevils by gen- 
eral habits of groAvth ; (2) those Avhich exclude the Aveevils, or at 
least hinder their operations in the buds and bolls; (3) those Avhich 
attract insect enemies such as the AA'eevil-eating kelep: (4) those 
Avhich prevent the development of the weevil larvae, even after the 
eggs haA^e been laid. 

ADAPTATIONS TO AVOID WEEVILS. 

1. Determinate growth. 

2. Earlj- bearing. 

^. Long basal branches. 

4. Early rejection of superfluous squares. 
^. Seasonal bearing of perennial varieties, 
fi. Prompt bearing after cutting back. 

7. Hairy stalks and leaf stems. 

5. I'endent bolls. 

0. Rapid growth of young bolls. 



SUMMARY or ADAPTATTONS. 78 

ADAPTATIONS TO EXCLUDE WKEVIl.S. 

1. luvolueral brnrts gi'owu toj^ether at base. 

'2. riosely a pi tressed margins of iiivolueral bracts. 

'.]. Margins of involucral bracts strongly laciniate and hairy. 

4. Unusual size and width of involucral bracts. 
r». Calyx produced into slender hairy lacinijie. 

<i. Persistent flowers. 

7. Oil glands i'i) of very young bolls. 

5. Thick-walled bolls. 

!). Tough linings of boll chambers. 

ADAPTATIONS ATTRACTIVE TO THE KELEP. 

1. Nectaries of leaves. 

2. Large outer nectaries of involucre. 

8. Large inner nectaries of involucre. 

4. Bractlets subtending inner nectaries. 

5. Continued secretion of nectar. 
(i. Hairy stalks and leaf stems. 

7. Dwarf, compact habits of growth. 

ArtAPTATIONS TO PREVENT DEVELOPMENT OF WEEVIL LARV.E. 

• 

1. Shedding of weevil-infested buds. 

2. Proliferation of internal tissues of buds. 

3. Proliferation from the walls of the bolls. 

4. Absence of oil glands over dissepiments. 

5. Growth of lint on seed. 

6. Compacted seeds (Kidney cotton). 

7. Lint confined to outer end of seed (San Lucas Sea Island cotton). 

ADAPTIVE CHARACTERS OF DIFFERENT TYPES OF COTTON. 

The third standpoint for viewing the adaptive characters is that 
of the different types of cotton. All varieties share, to some extent, 
the older adaptive features, but the special characters are accentuated 
in different degrees in the various types. Our study has been directed 
toward the Kekchi variety, both on account of its relation to the 
keleps and because it has seemed to possess by far the largest series 
of adaptive features. But now that the existence of adajitations of 
practical value has been ascertained it will be necessary to canvass 
the field thoroughly. 

ADAPTATIONS OF KEKCHI COTTON. 

An enumeration of the adaptations of the Kekchi cotton is scarcely necessary, 
because that variety has nearly the whole series and most of them in a more 
accentuated form than the other types thus far studied. The few exceptions 
are noted below. 

ADAPTATIONS OF RABINAL COTTON. 

1. Prompt bearing after cutting back. 

2. Very hairy stalks, leaf stems, and involucral bracts. 

3. Closely appressed margins of Involucral bracts. 

4. Involucral bracts grown together at base. 



74 WEFA'rT.-RESTSTTXO ADAPTATIONS OF COTTON. 

ADAPTATIONS OK I'ACIIO.N' (OTION. 

1. Involucral bracts margiued with stift" lacini.r and l)iistles. 

2. Calyx large, the divisions slender and hairy. 

ADAPTATIONS OF SAN LUCAS SKA ISLAND tOTTON. 

1. Definite seasonal bearing. 

2. Lint confined to outer half ot seed. 
.'!. Proliferation in buds. 

4. Proliferation in bolls. 

ADAPTATIONS OK KIDNEY COTTON. 

1. Definite seasonal bearing. 

2. Seeds coiui)acted at center, covered with thick layer of lint. 

ADAPTATIONS OK UPLAND COTTON. 

1. Shedding of weevil-infested buds. 

This is the only weevil-resisting character in which the Upland varieties 
excel the Kekchi cotton, but. as already explained, the habit is of practical use 
only in dry climates. The Upland cottons share, however, a large number of 
the adaptations, though in a less degi*ee than in the Kekchi. Thus there is pro- 
liferation both in buds and in bolls, the stems and petioles are somewhat hairy, 
the habit of growth is somewhat reduced from the tree-cotton sta.ge, the nec- 
taries are often large and active, the involucral bracts are sometimes well 
folded together, etc. 

And now that the possibility of weevil resistance has been shown, 
variations may be found in all probability among our United States 
varieties which will enable Aveevil-resisting strains of the Upland 
sorts to be developed. • At this stage of the inquiry it is too much to 
hope that the Kekchi tyjDe Avill prove to be adapted to the wide 
diversity of conditions to be found in the cotton .belt. P^ither the 
Kekchi or the native cottons, or both, are likely to'^^equire extensive 
modification before the full value of the weevil-resisting adaptations 
can be realized. 

CONCLUDING REMARKS. 

The protection afforded by the weevil-resisting adaptations is 
most effective at the two ends of the period of development, but con- 
tinues in varying degrees from the yoimg bud to the ripe boll. Under 
favorable conditions an extremely small proportion of the w^eevil 
eggs develop to maturity. Instead of a single attack being fatal to 
a bud or boll, the same fruit at its different stages may resist -numerous 
punctures and egg-layings. The young bud is protected for a time 
by the closed involucre. After the weevils have gained entrance the 
first egg, and often the second or third, may be rendered harmless 
through the proliferation of the bud in its younger stages. Pro- 
liferation becomes less certain as the bud increases in size, but if egg 
laying be delayed a fe^v days too long the development of the larvtr 



CONOLUDTNO EEMARKS, 75 

is rendered iiii|)()ssil)l(' \)y (he oix-iiiiiii- «»' t'"' ll<»\vt'r. Then ensue:s 
aiiotlu'i- iK'iiod of iiiuiiunity while the withered flower reinaiiis in 
phice and while the bolls are still too small to be attacked. Between 
abont the (luarter and the three-(inarter size the bolls can still be 
parasitized, though proliferation reduces the successful attempts to a 
very small percentage. But after the lint has grown out, the lining- 
has hardened, and the walls have become thick, the boll is well-nigh 
impregnable, though the surface may be roughened by a dozen or 
a score of warts, which mark the location of as many persistent but 
ineffectual attempts to gain entrance. 

As an instance of adaptive specialization the cotton plant seems des- 
tined to a very high rank. The development of such a series of pro- 
tective characters can scarcely be explained except upon the suppo- 
sition that the culture of cotton in Guatemala is extremely ancient, 
and of this there are many other indications. 

The practical utilization of these protective characters in the cotton 
industry of the United States may require the solution of many pre- 
liminnry problems of acclimatization and adaptation, as well as of 
physiology and cultural methods. The proliferation characters, for 
example, appear to be much more pronounced in some varieties than 
in others, but they are also affected, probably to a very considerable 
extent, by conditions of climate or soil Avhich check the growth of 
the plant or cut down its water sup})ly and thus reduce the nornuil 
turgidity of the tissues." 

The Aveevil-resisting characters are nnich more highly developed in 
the variety of cotton cultivated by the Kekchi Indians of eastern 
Guatemala than in any other type yet known, and it produces also 
large bolls and lint of good length and quality, so that it may be of 
value in the United States. But even though the Kekchi cotton in 
its present form should prove, for any reason, not to be adapted to 
cultural conditions in the United States, it demonstrates, at least, the 
fact that the Ujiland type of cotton is capable of assuming other 
characters which will render it far better adapted to cultivation in 
the presence of the boll weevil than the varieties hitherto grown in 
the United States. 

a That the transfer to Texas will not rlestroy the proliferating habit of the 
Kekchi cotton is shown by the following report from 'Mv. McLaehlan : 

" On the 28cl of August Mr. Kinsler and I made a comparative examina- 
tion of four varieties of cotton at Mackay, Tex., to determine the nature of 
their proliferation. Rows of Kekchi cotton from Secanquim and Lanquin, and 
two of native Upland varieties (Parker and King) were compared. The results, 
in brief, are that in squares the Kekchi cotton proliferated much more readily 
than did the native varieties. In the bolls all four varieties were about equally 
active in this protective adaptation. The extent of proliferation in the Guate- 
malan bolls was, if different in any way. somewhat greater than in the native 
\ arieties." 



76 WEEVTL-RESTSTTXO ADAPTATIONS OF COTTON. 

No end is in sight of th(> new problems and adjustments of cotton 
culture occasioned by the invasion of the weevils, and no assurances 
can be given in advance regar(Hng the utility of the weevil-resisting 
adaptations, any more than with the kele}), or so-called '" (iuatemalan 
ant." Both have a present value, however, in proving that the weevil 
is no invulnerable dragon which it is hopeless to resist. Instead of 
having no enemies, as long supposed, the Aveevil is regularly preyed 
upon by the active and efficient kelep. And instead of there being 
no remedies which can l)e used against the weevil, it is now found 
that the cotton plant itself has a whole series of weevil-resisting 
characters — a whole boll weevil armory, as it were, from which we 
may select and sharpen the Aveapons which prove best suited to our 
purposes. 

The weevil period of each year, that in which the damage is done, 
extends from the time when the squares are lai'ge enough for egg 
laying to the period Avhen a full crop would normally be set. If the 
value of the cotton croj) be divided by the number of days of this 
period, the result will show the value of each day of protection. It 
has been estimated by Mr. W. I). Hunter that the l)oll weevil damaged 
the cotton crop in 1904 to the extent of $20,000,000. It is therefore 
a very conservative estimate that when the pest shall have spread 
over the other cotton-growing States the damage will be well beyond 
a million dollars a day for the growing season — in unfavorable years 
probably two million dollars or more a day. P^ach day of protection 
Avhich can be secured by the utilization of weevil-resisting adapta- 
tions will have, therefore, very definite and considerable value, so that 
the study and perfection of this group of characters are sure to be 
the objects not only of formal scientific study on the part of special- 
ists but of general interest and consideration on the part of the prac- 
tical cotton-growing public. 



PLATES. 



77 



DESCRIPTION OF PLATES. 

Plate I. (Frontispiece.) Valley at Secanquliii. Alta Vera l*az, (iuatemala. the 
scene of experiments with weevil-resisting cotton. 

Plate II. Fig. 1. — Mature plant of Kekchi cotton, to show small size and 
determinate habits of gi'owth, compact foliage, and long basal bi-anches. 
Fig. 2. — I'lant shown in figure 1. opened to show numerous large bolls and 
habit of fruiting on basal branches. 

Plate III. Involucres of Kekchi cotton, opened to show external and internal 
nectaries, bracts, and bractlets. (Natural size.) 

Plate IV. Fig. 1. — Involucres of Rabinal cotton, showing connate and closel.v 
appressed involucral bracts. (Natural size.) Fig. 2.— Open involucres of 
Egyptian cotton. (Natural size.) 

Plate V. Fig. 1. — Young buds of Kekchi cotton, showing numerous weevil punc- 
tures. The buds were split in half so that the full number of punctures 
could be seen. (Natural size.) Fig. 2. — Buds of Kekchi cotton (same as 
fig. 1), showing successful proliferations. (Natural size.) 

Plate VI. Large buds of Kekchi cotton, the distortion indicating proliferation. 
(Natural size. ) 

Plate VII. Weevil-infested bolls of Kekchi cotton, showing larger number of 
punctures along the middle line of the carpel, where the oil glands are 
absent. (Natural size.) 

Plate A'III. Carpels of Kekchi cotton, showing method of proliferation. 
(Natural size.) 

Plate IX. Fig. 1. — Kekchi cotton, successive stages of the boll. Fig. 2. — 
Kekchi bolls (right): King bolls (left), to show comparative size. (Re- 
duced to about one-half natural size.) 

Plate X. Fig. 1. — Rabinal cotton, showing foliage, connate bracts, and weevil- 
infested bolls. (Reduced.) Fig. 2. — Bolls and seeds of Kidney cotton, 
showing oil glands and protective arrangement of lint and seeds. 
( Reduced. ) 



Bui. 88, Bureau of Plant Industry, U, S Dept of Agriculture 



Plate II. 





Bui. 88, Bureau of Plant Industiy, U. S. Dept. of Agriculture. 



Plate 111. 




Involucres of Kekchi Cotton, Showing Nectaries and Bractlets. 
(Natural size.) 



Bui. 88, Bureau of Plant Industry, U. S, Dept. of Agriculture. 



Plate IV. 




Fig. 1.— Involucres of Rabinal Cotton, Showing Connate and Appressed 

Margins. 

(Natural size.) 




FiQ. 2.— Open Involucres of Egyptian Cotton. 
(Natural size.) 



Bui. 88, Burpau of Plant Industry, U. S. Dept of Agriculture. 



Plate V. 





Fig. 1.— Young Buds of Kekchi Cot- 
ton WITH Weevil Punctures. 

(Natural size.) 



FiQ. 2.— Buds of Kekchi Cotton 
WITH Proliferation. 

(Natural .size.) 



Bui. 88, Buieau of Plant Industry U. S. Dept. of Agriculture. 



Plate VI. 




Large Buds of Kekchi Cotton with Proliferation. 
(Natural size.) 



Bui 88, Bureau of Pla-Tt Industry, U. S. Dept. of Agriculture. 



Plate VII. 




Weevil-infested Bolls of Kekchi Cotton. 
(Natural size ) 



Bui. 88, Bureau of Plant Industry, U. S. Dept. of Agriculture. 



Plate VIII. 




Carpels of Kekchi Cotton, Showing Proliferation. 
(.Natural size.) 



Bui. 83, Bureau of Plant Industry, U. S. Dept. of Agriculture. 



Plate IX, 




^ 9 



?? C) 




reau nf Plant Industry, U. S. Dept. of Agriculture. 



Plate X. 





INDKX 



Page. 

Abbasi cotton, flaring of squares 40 

Acacia, symbiotic specialization 29 

Acclimatization of Kekchi cotton 17 

Acconnnodation, direct responses to external conditions 69 

Adaptation, discussion 68, 69 

explained by natural selection 68 

Adaptations, attractive to the kelep 73 

classification 72 

climatic effect 1 0, 4H, 44 

commercial value 76 

historical treatment 72 

nature and causes 67 

periods when most effectiAc 74 

of Asiatic cottons unknown 32 

Kekchi and Rabinal cottons 73 

Kidney, Pachon, San Lucas Sea Island, and Upland cottons.. 74 

summary 72 

to avoid weevils 72 

exclude weevils 73 

prevent development of weevil larva* 73 

Adaptive characters, extent 69 

origin -. 67 

Aidin cotton, character 53 

Allen cotton, earlier than King in Guatemala 17 

Anthonoraus, behavior of species related to boll weevil 48 

Antidromy in cotton 19 

Antigua, Guatemala, culture of brown cotton 70 

Ants caring for plant lice 39 

injurious to cotton 39 

no protection against weevils 39 

plants domesticated by 29 

Aphids injurious to cotton 39 

Aphis Qossf/pii, infesting plants at liabinal, Guatemala 39 

Arid climate, inactive nectaries an adaptive result 24 

regions, behavior of cotton -1 3, 44, 45 

type of plant adapted : 20 

Artificial selection, an indefinite term 70 

Ashmead, William H., ants identified 39 

Asiatic cottons, comparison with other varieties . . , 53 

nectaries 28, 31 

Bacterial diseases following weevil injuries 62 

Bidens pilosa, nectar produced 36 

Birds, value as weevil destroyers 42 

Boll weevil larvae, adaptations to ])revent development 73 

behavior in Guatemala and Texas 47 

destruction by drying out of squares 43 

proliferation 46 

development in bolls 46 

effect of opening of flowers 47, 63 

rapid development in buds 63 

weevils, absence from Eastern Hemisphere 32 

Mexican plateau region 11 

adaptations to avoid 72 

exclude 73 

aid to cross-fertilization 55 

79 



80 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

Boll weevils — Continued. Page. 

bacterial diseases following injuries 62 

behavior in aVjsence of keleps 24 

on foot 25 

within bolls 59 

best conditions for perpetuation 70 

change of habits 63 

destruction by chickens and turkeys 24 

determination of life cycle in bolls and squares 64 

development of pollen-eating habit 63 

diverse habits of males and females 27 

diversity in size 64 

effect on unprotected cotton field 35 

under favorable conditions 69 

eggs, fate 58 

exclusion from large bolls 59 

feeding in bolls 61 

general effect on cotton plants 10 

in fields cultivated by Indians 35 

injuries in Guatemala 47 

injurious nature unknown to Indians 71 

^ mortality in spring 14 

not attracted by nearest relatives of cotton 69 

pollen diet 55 

preference for upper portion of plant 27 

selective influence 10 

self-destruction 34 

short-season varieties of cotton for control 22 

starvation 12, 14 

Bolls, diseases from superfluous nectar 28 

efficiency of adaptive characters 61 

fed upon by boll weevils .- 61 

feeding punctures 61 

infestation by weevils 55 

injured, discoloration 56, 59, 62 

Kekchi cotton, descriptit)n 16 

immunity 56 

linings of chambers, toughness as protection from boll weevil 56 

normal, absence at Rabinal, Guatemala 24 

oil glands 53 

outer walls, proliferation 58 

variation in thickness 56 

pendent, discussion 27 

periods of iuununity 74, 75 

position 27 

proliferation 59 

in relation to that of buds 64 

protection 51 

unconscious selection for uniform ripening 11 

very young, iuununity 52 

weevil punctures i 61 

weevil-proof lining 57 

young, rapid growth 55 

Bractlets of involucre 33 

Bracts, appressed margins 38 

dimensions 40 

flaring 40 

involucral, grown together 37 

hairy margins 41 

lacinia' 43 

of Kekchi cotton 16 

protective feature of lajge size 39 

Branches, long basal, disadvantages of 20 

of Kekchi cotton 19 

of cotton, compared witli those of otlier plants 19 

dimorphic 19 



INDEX. • 81 



Brown cotton, origin - ~_p 

preference of Indians^ 70 

Brues, C. T., observations 52 

Buds, breeding in, a derived habit 62 

falling in Kekchi cotton 20 

floral, dimensions -10 

method of rejection 21 

ovaries of, attacked by weevils 48 

parasitized, l)ehavior _ 43 

periods of immunity "4, / o 

persistence of injured 4 (^ 

proliferation 46 

causes and conditions 49 

in relation to that of l)olls . .■ 64 

protection by involucre 39, 41 

recovery from weevil punctures 41 

superfluous 21 

detrimental 22 

weevil-infested, shedding "4 

Cacao branches compared with cotton 19 

Cajabon, Guatemala, cotton grown in vicinity 15 

planting of brown cotton 70 

Cecropia, symbiotic specialization 29 

Chickens, boll weevil destroyers 24 

Climate, effect of change on Upland varieties 16 

on earliness •- 17 

germination of seed 15 

Climatic conditions, effect on United States varieties ^ 17 

effects on adaptations 10, 43, 44 

variations in cottou 17 

Cluster cotton, discussion 28 

origin 70 

pendent bolls 28 

rejection of buds 21 

variety of King cotton 17 

Coffee branches compared with cotton 19 

Cold, effect on tropical varieties 18 

weevils 12,13 

Collins, G. N. , observation 54 

Conscious selection 70 

Corn, effect of clianged conditions 18 

Cotton aphis, infesting cotton - 39 

production, prol)al)le extension 44 

short-season varieties 12, 14, 22 

stimulus of new conditions 17 

Cross-fertilization aided by Ix >! 1 weevils 55 

effect of sinndtaneous blossoming 23 

secured through nectar 29 

Cuba, native cottons 23 

Culture of cotton, methods, in eastern Guatemala 19 

on Pacific slope of Guatemala 70 

Mexico 45 

Determinate growth of Kekchi cotton 11 

habit, disadvantages of early planting avoided 14 

primary branches a factor : - - - 20 

Dimorphic branches 19 

Dry climate, region, etc. See Arid. 

Dwarf cotton, effect on cultural methods 19 

habit of Kekchi cotton 11 

Earliness, effect of development of primary branches ' 20 

climatic conditions 12, 17 

not shown 1 )y date of flowering 13 

Early bearing, facilitated by long basal branches 19 

planting, disadvantages 14 

9962— No. 88—05 m 6 



82 WEEVIL-EESISTING ADAPTATIONS OF COTTON, 

Page. 

Early planting, discussion 13 

essential in southern Texas 12 

Egg puncture sealed by weevil 61 

Eggs of boll weevils, encystation 58, 61 

Egyptian cottons, immunity from bolhvorm 53 

involucral bracts 37 

less hairy than Upland varieties 25 

not immune to boll weevil 42 

oil glands 53 

of American origin 9 

precocious in Guatemala 17 

preference of weevils 26 

proliferation 50 

susceptibility to injury 42 

Environment not actuating cause of evolutionary change 68 

Evolution, illustration of inlluence of natural seiecti(jn 71 

Evolutionary origin of external nectaries 31 

Fertilization, discussion 52 

prevention by rain 21 

Field cultures, failure in plateau region of Guatemala 25 

Flower bud, position , .• 20 

Flowering period, short 23 

Flowers, failure of pollination 51 

keleps imprisoned 29 

of Kekchi cotton, color 54 

Kidney cotton, color 53 

opening, effect on larvfe 47, 63 

persistence 51 

position 27 

Foliage, compact, effect on keleps 26 

Food, change, advantage to plants and animals 26 

Fungi, growth in nectaries 30 

(Termination, cotton seed in Guatemala 15 

(iossiipium harbadense, origin 8 

herhaceum, Asia Minor A'arieties 53 

confusion with G. Jiirsutum 9 

nectaries 31 

peruvianidn, specific validity 67 

Growth, alternating periods in tropical plants 23 

utility of acceleration 55 

Guatemala, central plateau 24 

eastern, climate 12 

methods of cotton cuUure. „ 19, 70 

nature of the country 15 

field experiments 34 

importation of foreign thread 24 

Indian methods of cultivation 12 

western, cotton 25, 70 

Guatemalan conditions, effect on United States varieties 17 

cottons, preference of keleps 25 

Hairs, cotton plant, assistance to keleps 25 

Hairy Guatemalan varieties of cotton 25 

stalks and leaf stems of cotton 25 

Heredity, mechanism 68 

Hibiscus, involucral appendages of species 33 

nectaries of species 32 

species not attractive to boll weevil 69 

Hinds, W. E., observations 25, 42, 43, 44, 55, 61, 62, 64 

Howard, L. O. , observations 45 

Humid districts, behavior of cotton 43, 44 

Hunter, W. D., observations 14, 25, 42, 43, 44, 48, 55, 61, 64, 76 

Immunity of buds and bolls, periods 74, 75 

Inbreeding of cotton by Indians 15 

Indeterminate varieties unsuited to early destruction of plants 13 



INDEX. 83 

Pace. 

Indian methods of cotton culture 11, 35 

names of cotton 53, 70 

Indians, agricultural habits 11, 15, 35, 48 

cotton culture 11, 35, 71 

cultivation of peppers 11 

customs at Ral)inal, Guatemala 24 

formation of new varieties 15, 71 

Guatemalan, observations on boll weevils 66 

of Alta Vera Paz, ( ruatemala, characteristics 71, 72 

selections of cotton 15, 16, 71 

utilization of cotton 45 

Interbreeding necessary to vigor 68 

Involucral appendages of plants related to cotton 33 

bracts of Pachon cotton 25 

Involucre, as a protective structure 37 

bractlets 33 

external nectaries, discussion 31 

inner nectaries, discussion 31 

protection to inside nectaries 28 

protective value 37 

Involucres, closed, advantages 38, 41 

Egvptian cottons 41 

Kekchi cotton 37, 39, 40 

Kidney cotton 32 

open, advantage 42 

Rabinal cotton 37 

Sea Island cotton, attractive to keleps 26 

Upland cottons 38 

value in jirotecting buds 39, 41 

Irrigation, effects 45 

Ixcaco cotton in Guatemala 70 

Jannovitch cotton compared with Allen 17 

proliferation 50 

Jewett cotton, dimensions of buds and bracts 40 

Kekchi cotton, adaptations 73 

at northern limit of cotton culture 18 

behavior, in Texas 17 

bolls, variation in thicknesg of walls 56 

characteristic feature 20 

comparison with other varieties, at Lanham, Md 18 

date of planting in Guatemala 15 

developed in weevil-infested regions 4 

distinct type of (joiiftj/pmm hirsutum 8 

effect of crowding on character 20 

fruiting 17 

habits of growth 15 

in the United States 17 

most promising short-season variety 22 

quality of lint 7 

rapidity of development 55 

shortness of season, explanation 11 

stems, petioles, leaves, and l)olls 16 

tolerance of cold 15 

variations 15 

weevil resistance, high value 11 

Keleps, absent from Eastern Hemisphere 32 

adaptations, attractive 73 

definitely attracted to cotton plants 35 

effect of dense foliage 26 

habitat extension 36 

hairs of cotton plant, assistance in climbing 25 

imprisonment in flowers 29 

preference for Egyptian and Sea Island cotton and Biilens pll(mt. . 26, 36, 37 

protection to cotton 8, 34, 35 

unknown to European residents in Guatemala 71 



84 wp:p:vil-resisting adaptations of cotton. 

Page. 

Keleps, usefulness in comparison with ants 39 

value known by Indians 71 

visitation of other nectar-bearing plants than cotton 36 

Kidnej' cotton, adaptations 74 

at Trece Aguas, Guatemala 32, 53 

Tucuru, Guatemala 24, 66 

characters 67 

cultural value 67 

of A nierican origin 9 

oil glands 53, 54 

origin of name 9 

protective features 42 

seed arrangement 66 

thin outer wall of boll 66 

King cotton, l)ehavior in Guatemala 17 

cluster variety 17 

dimensions of buds and bracts 40 

flaring of squares 40 

large nectaries 31 

proliferation 60 

rapidity of development 55 

Kinsler, J. H., observations 17, 29, 37, 47, 50, 51, 55 

plants cultivated in Guatemala 15 

Lacinife of involucral bracts 43 

Lanham, Md., experiments 18, 25, 43 

Lanquim, Guatemala, planting of brown cotton 70 

Large varieties, disadvantages 19 

Late planting in northern localities 13 

Leaves, Kekchi cotton 16 

nectaries, general discussion 30 

Leavitt, R. G. , principle of translocation of characters 70 

Limbless variety of King cotton 17 

Lint, disadvantages 65 

protection of seeds 65, 66 

Locks, number in Kekchi cotton 16 

Mackay , Tex. , examination of cotton 75 

Maxon, W. R., cotton obtained 25 

oliservations , 70 

McLachlan, Argyle, observations 18, 25, 41, 47, 57, 60, 61, 75 

Melanthera deltoidea visited l)y keleps 37 

Mexican plateau, absence of weevils 11 

region, advantages 43 

Mexico, cotton culture 45 

Mit Afifi cotton, oil glands 53 

Molds, growth in nectaries 30 

Moqui Indian cotton, character 52 

jNIutations in Kekchi cotton 16 

Natural selection by boll weevil 54, 69 

cotton 9 

conscious and unconscious 70 

effect of oil glands 54 

illustration of influence in evolution 71 

in simultaneous flowering ■ 23 

not actuating cause of evolutionary change 68 

the explanation of adaptation 68 

Nectar, continued secretion by plants 32 

purpose 2S 

secretion in Kekchi and Upland cottons 32 

on bolls 33 

Nectaries, external, discussion 31 

position in pendent bolls 27 

secretion 27 

extrafloral, connection with bacterial diseases 62 

discussion 28 

functions 29 



INDEX. 85 

Page. 

Nectaries, extrafloral, in Kekclii cotton 34 

floral, no connection with weevil resistance 29 

homology 32 

inactive, of Rabinal cotton 24 

inner, bractlets subtending 33 

connected with drooping habit 28 

of involucre, discussion 31 

of different varieties 31, 32 

Kekchi cotton 16 

leaves, general discussion 30 

species of Hibiscus 32 

Oil glands, of bolls 53 

protective feature 52, 54 

Okra cotton, origin 70 

Old World cottons. See Asiatic. 

Origin of cottons in arid regions 21 

improved varieties of cotton 70 

Upland varieties of cotton 10, 44 

Pachon cotton, adaptations 74 

characters 34, 43 

comparison in Texas and jNlarylanA 18 

• hairiness 25 

involucral bracts 25 

Palmer, Dr. Edward, discovery of weevil 45 

observations on cotton 45 

Paris green, effects on boll weevils 14 

I'aritium, species not attractive to boll weevil 69 

Parker cotton, dimensions of buds and bracts 40 

experiments 41, 57, 60 

flaring of squares 40 

proliferation 60 

Pendent bolls, discussion 27 

Peppers, importance to Indians 11 

Perennial cottons, annual cutting back 24 

not likely to be of use in the United States 67 

seasonal bearing 23 

Pergande, Theodore, identification of aphids 39 

Peruvian cotton in Texas ] 7 

Petals, smoothness an obstacle to keleps 26 

Petioles, Kekchi cotton 16 

Pittier, H. , observations 26, 39, 46 

Planting, date in Guatemala 19 

late in northern localities 13 

Plant lice injurious to cotton 39 

Plants, destruction in the fall, difficulty 22 

Pollen, diet of weevils .55 

eaten by weevil larvte 47 

necessity for sexual maturity of weevils 55 

Pollen-eating haVjit, development 63 

Poneridie, nectar collected 30 

Proliferation, advantage only under conscious selection 71 

best weevil-resisting adaptation 9 

diminution of power in larger buds 51 

effect of dry weather 60 

efficiency 46 

from staminal tube 49 

wall of boll 58 

in buds and l^olls, relation 64 

Kekchi cotton 46, 49, 75 

King cotton 60 

Parker cotton 60 

varieties other than Kekchi 50 

of bolls 55, 56, 59 

bud, cau.ses and conditions 49 

corolla 48 

internal tissues of buds 46 



86 WEEVIL-RESISTING ADAPTATIONS OF COTTON. 

Page. 

Proliferation, probable effects of culture 50 

summary of results of study .-49 

time required 60 

value 65 

Protection afforded by adaptations, commercial value 76 

when most effective 74 

the involucre 37 

tough linings of chambers of bolls 56 

by keleps, efficiency 34, 35 

of seeds by lint 65 

Protective characters, first originated by cotton plant 68 

general 11 

of bolls 51 

value of involucre 37 

Quaintance, A. L., observations 52 

Rabinal cotton, adaptations 73 

bolls fed upon by boll weevils 61 

characters 41 

hairiness - 25 

involucres 37, 38 

nectaries 31 

Guatemala, ants - S9 

cotton culture 9, 38 

customs of Indians 24 

Rain, effect at time of flowering 21 

Redshank cotton, characters 53 

large nectaries 31 

Retalhuleu district of (.Guatemala, cotton planted 25, 34 

Rivers cotton, character in Guatemala 17 

Rul)ber, Central American, branches compared with those of cotton 19 

Sajal, plant often visited by keleps 37 

Salama, Guatemala, cotton culture of Indians 24 

San Lucas, Guatemala, Sea Island cotton 24 

adaptations 74 

attacked by other insects 32 

disco veiy 50 

nectaries 32 

Schwarz, E. A., observations 42, 48 

on Cuban cottons 23 

Sea Island cotton, Guatemalan, discovery 50 

nectaries 32 

of San Lucas, Guatemala, annual flowering 24 

cottons, comparison of petals with Upland varieties 26 

flaring of squares 40 

involucral bracts 37, 38 

lacking in protective features 4 

less hairy than Upland varieties 25 

not immune to boll weevil 42 

oil glands 53 

origin 8 

precocity in Guatemala 17 

smoothness a disadvantage to keleps 25 

Secanquim, Guatemala, cotton grown in vicinity 15 

experiments 39, 41 

Seed, low germination in Guatemala 15 

Seeds, protective arrangement in Kidney cotton 66 

Selection, conscious, unconscious, natural, and artificial, discussion 11, 70, 71 

in cotton, time required 10 

provided by boll weevil 10 

Selective influence of boll weevil 10 

Short season varieties of cotton 1 2, 14, 22 

Solenopsis picea, ant inhabiting Rabinal cotton 39 

Specific type, generalized, the product of diversity and interbreeding 68 

Squares, boll weevil injuries 41 

flared and fallen, countings 45 

flaring -10, 41 



INDEX. O i 

Page. 

Squares, multiplication in cluster cottons 28 

small, ])ree(ling places for weevils 11 

superfluous, early rejection 20 

weevil-infested, shedding 43, 74 

Staminal tube, proliferation 49 

Stipules of outer bracts represented by bractlets 33 

Stormproof varieties of cotton 27 

Superfluous buds, discussion 21 

Symbiotic specializations between plants and animals 29 

Tap'moma ramulonun, ant inhabiting Rabinal cotton 39 

Temperatures at localities where Kekchi cotton is grown 15 

Terrell, Tex. , experiments : .- - 52 

Texas, early advent of weevils 9 

southern, method of checking weevil 12 

Thespesia, species not attractive to boll weevil 69 

Top crop, effect of weevil 22 

Tree cottons, dimensions 23 

discussion 17 

immunity to weevils, reported 23 

in Guatemala 12 

infestation by weevils 8 

Mexican, nectaries 30 

rejection of buds 21 

weevil adaptations 23 

{See also Perennial cottons.) 

Trelease, William, observations 33 

Troi^ical A merica, field for experiments 9 

Tshubai, plant protected by the kelep 36 

Tucuru, Guatemala, Kidney cotton 24, 66 

Turkeys, boll weevil destroyers 24 

Tyler, F. J. , observations 28 

United States cotton varieties, effect of Guatemalan conditions 17 

Upland cottons, adajjtations 74 

eff ett of change of climate 16 

indeterminate habit in United States varieties 13 

native in Central America 10 

origin : . 10, 44 

preference of keleps 25 

secretion of nectar 32 

Variations, climatic, in cotton 17 

in Kekchi cotton , 15 

Variegation in Kekchi cotton IH 

Varieties, new, formation by Indians 15 

Victoria, Tex. , experiments : 60, 61 

Volunteer cotton, absence in eastern Guatemala 12 

breeding of weevils 12 

AVeather, dry, effect on crop 13 

exclusion of boll weevil from Mexican plateau 11 

Webber, H. J. , statements 13, 42 

Weaving by Guatemalan natives, use of foreign thread 25 

Weevil. See Boll weevil. 

Weevil-proof lining of bolls 57 

Weissman, Professor, doctrine of inheritance 68 

Winters, severe, no protection from weevils 12 

o 



c 



LB Mr '08 



^ 



